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	$160.31	3.561%	$166.0186	$166.02	$166.00	$166.00
Purchase #2	$56.92	9.800%	$62.4982	$62.50	$62.50	$62.50
Purchase #3	$100.59	10.252%	$110.9025	$110.90	$110.90	$110.90
Purchase #4	$225.46	10.138%	$248.3171	$248.32	$248.30	$248.30
Purchase #5	$130.31	12.288%	$146.3225	$146.32	$146.30	$146.30
Purchase #6	$106.33	11.194%	$118.2326	$118.23	$118.25	$118.20
Purchase #7	$222.33	13.785%	$252.9782	$252.98	$253.00	$253.00
7 purchase totals =	$1,002.25		$1,105.2697	$1,105.27	$1,105.25	$1,105.20