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	$65.62	3.148%	$67.6857	$67.69	$67.70	$67.70
Purchase #2	$41.29	12.314%	$46.3745	$46.37	$46.35	$46.40
Purchase #3	$59.56	11.118%	$66.1819	$66.18	$66.20	$66.20
Purchase #4	$40.54	6.740%	$43.2724	$43.27	$43.25	$43.30
Purchase #5	$217.67	10.720%	$241.0042	$241.00	$241.00	$241.00
Purchase #6	$55.95	9.756%	$61.4085	$61.41	$61.40	$61.40
Purchase #7	$219.57	10.786%	$243.2528	$243.25	$243.25	$243.30
7 purchase totals =	$700.20		$769.1800	$769.17	$769.15	$769.30