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	$40.27	4.115%	$41.9271	$41.93	$41.95	$41.90
Purchase #2	$202.32	10.778%	$224.126	$224.13	$224.15	$224.10
Purchase #3	$149.46	6.567%	$159.275	$159.28	$159.30	$159.30
Purchase #4	$179.34	6.761%	$191.4652	$191.47	$191.45	$191.50
Purchase #5	$248.25	10.845%	$275.1727	$275.17	$275.15	$275.20
Purchase #6	$50.69	3.112%	$52.2675	$52.27	$52.25	$52.30
Purchase #7	$105.73	9.567%	$115.8452	$115.85	$115.85	$115.80
7 purchase totals =	$976.06		$1,060.0787	$1,060.10	$1,060.10	$1,060.10