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	$243.62	8.482%	$264.2838	$264.28	$264.30	$264.30
Purchase #2	$166.26	3.255%	$171.6718	$171.67	$171.65	$171.70
Purchase #3	$13.47	10.558%	$14.8922	$14.89	$14.90	$14.90
Purchase #4	$161.98	13.613%	$184.0303	$184.03	$184.05	$184.00
Purchase #5	$81.94	4.766%	$85.8453	$85.85	$85.85	$85.80
Purchase #6	$113.59	11.713%	$126.8948	$126.89	$126.90	$126.90
Purchase #7	$185.65	12.216%	$208.329	$208.33	$208.35	$208.30
7 purchase totals =	$966.51		$1,055.9472	$1,055.94	$1,056.00	$1,055.90