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	$176.43	11.857%	$197.3493	$197.35	$197.35	$197.30
Purchase #2	$58.92	9.344%	$64.4255	$64.43	$64.45	$64.40
Purchase #3	$210.56	5.616%	$222.385	$222.39	$222.40	$222.40
Purchase #4	$168.29	8.268%	$182.2042	$182.20	$182.20	$182.20
Purchase #5	$134.75	8.459%	$146.1485	$146.15	$146.15	$146.10
Purchase #6	$165.45	6.629%	$176.4177	$176.42	$176.40	$176.40
Purchase #7	$105.71	5.216%	$111.2238	$111.22	$111.20	$111.20
7 purchase totals =	$1,020.11		$1,100.1540	$1,100.16	$1,100.15	$1,100.00