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	$40.47	13.341%	$45.8691	$45.87	$45.85	$45.90
Purchase #2	$40.29	10.488%	$44.5156	$44.52	$44.50	$44.50
Purchase #3	$232.53	4.472%	$242.9287	$242.93	$242.95	$242.90
Purchase #4	$222.47	5.767%	$235.2998	$235.30	$235.30	$235.30
Purchase #5	$179.95	13.549%	$204.3314	$204.33	$204.35	$204.30
Purchase #6	$61.83	9.199%	$67.5177	$67.52	$67.50	$67.50
Purchase #7	$202.33	4.711%	$211.8618	$211.86	$211.85	$211.90
7 purchase totals =	$979.87		$1,052.3241	$1,052.33	$1,052.30	$1,052.30