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	$52.33	9.539%	$57.3218	$57.32	$57.30	$57.30
Purchase #2	$99.92	10.214%	$110.1258	$110.13	$110.15	$110.10
Purchase #3	$94.40	5.514%	$99.6052	$99.61	$99.60	$99.60
Purchase #4	$47.55	11.312%	$52.9289	$52.93	$52.95	$52.90
Purchase #5	$50.53	8.383%	$54.7659	$54.77	$54.75	$54.80
Purchase #6	$194.28	7.454%	$208.7616	$208.76	$208.75	$208.80
Purchase #7	$104.78	13.635%	$119.0668	$119.07	$119.05	$119.10
7 purchase totals =	$643.79		$702.5760	$702.59	$702.55	$702.60