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	$185.47	3.692%	$192.3176	$192.32	$192.30	$192.30
Purchase #2	$55.92	6.300%	$59.443	$59.44	$59.45	$59.40
Purchase #3	$197.87	10.579%	$218.8027	$218.80	$218.80	$218.80
Purchase #4	$89.76	8.135%	$97.062	$97.06	$97.05	$97.10
Purchase #5	$239.74	3.282%	$247.6083	$247.61	$247.60	$247.60
Purchase #6	$172.76	10.680%	$191.2108	$191.21	$191.20	$191.20
Purchase #7	$71.76	9.682%	$78.7078	$78.71	$78.70	$78.70
7 purchase totals =	$1,013.28		$1,085.1522	$1,085.15	$1,085.10	$1,085.10