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	$63.53	12.561%	$71.51	$71.51	$71.50	$71.50
Purchase #2	$64.86	4.672%	$67.8903	$67.89	$67.90	$67.90
Purchase #3	$250.90	5.144%	$263.8063	$263.81	$263.80	$263.80
Purchase #4	$86.93	10.755%	$96.2793	$96.28	$96.30	$96.30
Purchase #5	$212.68	4.686%	$222.6462	$222.65	$222.65	$222.60
Purchase #6	$174.72	13.491%	$198.2915	$198.29	$198.30	$198.30
Purchase #7	$151.27	6.863%	$161.6517	$161.65	$161.65	$161.70
7 purchase totals =	$1,004.89		$1,082.0753	$1,082.08	$1,082.10	$1,082.10