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	$34.91	8.489%	$37.8735	$37.87	$37.85	$37.90
Purchase #2	$12.56	9.678%	$13.7756	$13.78	$13.80	$13.80
Purchase #3	$229.79	3.390%	$237.5799	$237.58	$237.60	$237.60
Purchase #4	$241.82	9.165%	$263.9828	$263.98	$264.00	$264.00
Purchase #5	$178.28	9.139%	$194.573	$194.57	$194.55	$194.60
Purchase #6	$91.95	9.399%	$100.5924	$100.59	$100.60	$100.60
Purchase #7	$244.38	13.736%	$277.948	$277.95	$277.95	$277.90
7 purchase totals =	$1,033.69		$1,126.3252	$1,126.32	$1,126.35	$1,126.40