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	$59.51	12.441%	$66.9136	$66.91	$66.90	$66.90
Purchase #2	$54.44	10.466%	$60.1377	$60.14	$60.15	$60.10
Purchase #3	$8.54	9.111%	$9.3181	$9.32	$9.30	$9.30
Purchase #4	$8.36	11.127%	$9.2902	$9.29	$9.30	$9.30
Purchase #5	$51.58	5.809%	$54.5763	$54.58	$54.60	$54.60
Purchase #6	$115.33	7.122%	$123.5438	$123.54	$123.55	$123.50
Purchase #7	$33.27	13.687%	$37.8237	$37.82	$37.80	$37.80
7 purchase totals =	$331.03		$361.6034	$361.60	$361.60	$361.50