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	$65.77	3.216%	$67.8852	$67.89	$67.90	$67.90
Purchase #2	$222.76	4.751%	$233.3433	$233.34	$233.35	$233.30
Purchase #3	$222.49	5.764%	$235.3143	$235.31	$235.30	$235.30
Purchase #4	$218.46	4.843%	$229.04	$229.04	$229.05	$229.00
Purchase #5	$166.59	8.704%	$181.09	$181.09	$181.10	$181.10
Purchase #6	$122.88	8.329%	$133.1147	$133.11	$133.10	$133.10
Purchase #7	$99.51	5.559%	$105.0418	$105.04	$105.05	$105.00
7 purchase totals =	$1,118.46		$1,184.8293	$1,184.82	$1,184.85	$1,184.70