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	$246.68	3.841%	$256.155	$256.16	$256.15	$256.20
Purchase #2	$73.30	8.574%	$79.5847	$79.58	$79.60	$79.60
Purchase #3	$60.33	3.801%	$62.6231	$62.62	$62.60	$62.60
Purchase #4	$212.59	3.591%	$220.2241	$220.22	$220.20	$220.20
Purchase #5	$48.59	12.556%	$54.691	$54.69	$54.70	$54.70
Purchase #6	$92.54	4.221%	$96.4461	$96.45	$96.45	$96.40
Purchase #7	$128.47	11.220%	$142.8843	$142.88	$142.90	$142.90
7 purchase totals =	$862.50		$912.6083	$912.60	$912.60	$912.60