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	$186.65	11.869%	$208.8035	$208.80	$208.80	$208.80
Purchase #2	$188.25	4.465%	$196.6554	$196.66	$196.65	$196.70
Purchase #3	$222.32	4.244%	$231.7553	$231.76	$231.75	$231.80
Purchase #4	$228.89	8.838%	$249.1193	$249.12	$249.10	$249.10
Purchase #5	$53.26	11.368%	$59.3146	$59.31	$59.30	$59.30
Purchase #6	$143.67	8.148%	$155.3762	$155.38	$155.40	$155.40
Purchase #7	$18.34	9.779%	$20.1335	$20.13	$20.15	$20.10
7 purchase totals =	$1,041.38		$1,121.1578	$1,121.16	$1,121.15	$1,121.20