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	$40.61	12.449%	$45.6655	$45.67	$45.65	$45.70
Purchase #2	$73.48	11.288%	$81.7744	$81.77	$81.75	$81.80
Purchase #3	$205.31	9.409%	$224.6276	$224.63	$224.65	$224.60
Purchase #4	$219.95	6.780%	$234.8626	$234.86	$234.85	$234.90
Purchase #5	$115.45	3.809%	$119.8475	$119.85	$119.85	$119.80
Purchase #6	$205.29	7.114%	$219.8943	$219.89	$219.90	$219.90
Purchase #7	$93.61	10.439%	$103.3819	$103.38	$103.40	$103.40
7 purchase totals =	$953.70		$1,030.0538	$1,030.05	$1,030.05	$1,030.10