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	$34.83	6.513%	$37.0985	$37.10	$37.10	$37.10
Purchase #2	$221.60	9.469%	$242.5833	$242.58	$242.60	$242.60
Purchase #3	$170.39	5.207%	$179.2622	$179.26	$179.25	$179.30
Purchase #4	$30.55	6.740%	$32.6091	$32.61	$32.60	$32.60
Purchase #5	$184.27	8.254%	$199.4796	$199.48	$199.50	$199.50
Purchase #6	$141.43	8.154%	$152.9622	$152.96	$152.95	$153.00
Purchase #7	$186.27	7.218%	$199.715	$199.72	$199.70	$199.70
7 purchase totals =	$969.34		$1,043.7099	$1,043.71	$1,043.70	$1,043.80