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	$33.98	11.141%	$37.7657	$37.77	$37.75	$37.80
Purchase #2	$243.30	12.695%	$274.1869	$274.19	$274.20	$274.20
Purchase #3	$30.25	10.866%	$33.537	$33.54	$33.55	$33.50
Purchase #4	$66.86	7.308%	$71.7461	$71.75	$71.75	$71.70
Purchase #5	$213.71	12.545%	$240.5199	$240.52	$240.50	$240.50
Purchase #6	$132.68	10.591%	$146.7321	$146.73	$146.75	$146.70
Purchase #7	$222.55	12.871%	$251.1944	$251.19	$251.20	$251.20
7 purchase totals =	$943.33		$1,055.6821	$1,055.69	$1,055.70	$1,055.60