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	$152.91	10.233%	$168.5573	$168.56	$168.55	$168.60
Purchase #2	$229.65	7.816%	$247.5994	$247.60	$247.60	$247.60
Purchase #3	$43.84	13.412%	$49.7198	$49.72	$49.70	$49.70
Purchase #4	$237.78	9.591%	$260.5855	$260.59	$260.60	$260.60
Purchase #5	$64.48	10.775%	$71.4277	$71.43	$71.45	$71.40
Purchase #6	$204.80	8.714%	$222.6463	$222.65	$222.65	$222.60
Purchase #7	$81.65	13.797%	$92.9153	$92.92	$92.90	$92.90
7 purchase totals =	$1,015.11		$1,113.4513	$1,113.47	$1,113.45	$1,113.40