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	$43.63	4.513%	$45.599	$45.60	$45.60	$45.60
Purchase #2	$10.50	9.286%	$11.475	$11.48	$11.50	$11.50
Purchase #3	$155.54	4.231%	$162.1209	$162.12	$162.10	$162.10
Purchase #4	$74.34	10.432%	$82.0951	$82.10	$82.10	$82.10
Purchase #5	$121.40	4.301%	$126.6214	$126.62	$126.60	$126.60
Purchase #6	$64.25	4.760%	$67.3083	$67.31	$67.30	$67.30
Purchase #7	$246.97	11.313%	$274.9097	$274.91	$274.90	$274.90
7 purchase totals =	$716.63		$770.1294	$770.14	$770.10	$770.10