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	$210.59	10.869%	$233.479	$233.48	$233.50	$233.50
Purchase #2	$72.37	10.462%	$79.9413	$79.94	$79.95	$79.90
Purchase #3	$245.74	7.586%	$264.3818	$264.38	$264.40	$264.40
Purchase #4	$45.34	11.415%	$50.5156	$50.52	$50.50	$50.50
Purchase #5	$180.26	11.126%	$200.3157	$200.32	$200.30	$200.30
Purchase #6	$229.52	9.471%	$251.2578	$251.26	$251.25	$251.30
Purchase #7	$108.29	3.663%	$112.2567	$112.26	$112.25	$112.30
7 purchase totals =	$1,092.11		$1,192.1479	$1,192.16	$1,192.15	$1,192.20