Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.77	11.777%	$166.2906	$166.29	$166.30	$166.30
Purchase #2	$138.76	13.466%	$157.4454	$157.45	$157.45	$157.40
Purchase #3	$128.60	11.190%	$142.9903	$142.99	$143.00	$143.00
Purchase #4	$145.82	11.656%	$162.8168	$162.82	$162.80	$162.80
Purchase #5	$219.66	11.808%	$245.5975	$245.60	$245.60	$245.60
Purchase #6	$102.44	3.417%	$105.9404	$105.94	$105.95	$105.90
Purchase #7	$123.99	6.373%	$131.8919	$131.89	$131.90	$131.90
7 purchase totals =	$1,008.04		$1,112.9729	$1,112.98	$1,113.00	$1,112.90