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	$166.37	12.481%	$187.1346	$187.13	$187.15	$187.10
Purchase #2	$102.77	10.344%	$113.4005	$113.40	$113.40	$113.40
Purchase #3	$16.56	10.401%	$18.2824	$18.28	$18.30	$18.30
Purchase #4	$72.39	8.472%	$78.5229	$78.52	$78.50	$78.50
Purchase #5	$153.33	8.478%	$166.3293	$166.33	$166.35	$166.30
Purchase #6	$234.92	11.848%	$262.7533	$262.75	$262.75	$262.80
Purchase #7	$176.67	5.143%	$185.7561	$185.76	$185.75	$185.80
7 purchase totals =	$923.01		$1,012.1791	$1,012.17	$1,012.20	$1,012.20