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	$121.34	8.580%	$131.751	$131.75	$131.75	$131.80
Purchase #2	$108.39	9.645%	$118.8442	$118.84	$118.85	$118.80
Purchase #3	$40.52	11.190%	$45.0542	$45.05	$45.05	$45.10
Purchase #4	$78.83	13.111%	$89.1654	$89.17	$89.15	$89.20
Purchase #5	$174.99	12.160%	$196.2688	$196.27	$196.25	$196.30
Purchase #6	$110.86	5.471%	$116.9252	$116.93	$116.95	$116.90
Purchase #7	$66.69	5.201%	$70.1585	$70.16	$70.15	$70.20
7 purchase totals =	$701.62		$768.1673	$768.17	$768.15	$768.30