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	$105.41	12.331%	$118.4081	$118.41	$118.40	$118.40
Purchase #2	$108.73	9.705%	$119.2822	$119.28	$119.30	$119.30
Purchase #3	$25.25	10.190%	$27.823	$27.82	$27.80	$27.80
Purchase #4	$99.37	4.639%	$103.9798	$103.98	$104.00	$104.00
Purchase #5	$148.35	13.678%	$168.6413	$168.64	$168.65	$168.60
Purchase #6	$158.86	6.106%	$168.56	$168.56	$168.55	$168.60
Purchase #7	$232.42	6.396%	$247.2856	$247.29	$247.30	$247.30
7 purchase totals =	$878.39		$953.9800	$953.98	$954.00	$954.00