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	$88.77	8.462%	$96.2817	$96.28	$96.30	$96.30
Purchase #2	$40.86	13.515%	$46.3822	$46.38	$46.40	$46.40
Purchase #3	$229.43	11.224%	$255.1812	$255.18	$255.20	$255.20
Purchase #4	$48.83	3.828%	$50.6992	$50.70	$50.70	$50.70
Purchase #5	$63.63	6.618%	$67.841	$67.84	$67.85	$67.80
Purchase #6	$22.53	6.114%	$23.9075	$23.91	$23.90	$23.90
Purchase #7	$145.50	13.307%	$164.8617	$164.86	$164.85	$164.90
7 purchase totals =	$639.55		$705.1545	$705.15	$705.20	$705.20