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	$239.75	5.593%	$253.1592	$253.16	$253.15	$253.20
Purchase #2	$210.66	5.620%	$222.4991	$222.50	$222.50	$222.50
Purchase #3	$19.63	7.150%	$21.0335	$21.03	$21.05	$21.00
Purchase #4	$174.87	6.831%	$186.8154	$186.82	$186.80	$186.80
Purchase #5	$211.50	3.305%	$218.4901	$218.49	$218.50	$218.50
Purchase #6	$56.85	12.870%	$64.1666	$64.17	$64.15	$64.20
Purchase #7	$52.33	4.329%	$54.5954	$54.60	$54.60	$54.60
7 purchase totals =	$965.59		$1,020.7593	$1,020.77	$1,020.75	$1,020.80