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	$67.54	11.575%	$75.3578	$75.36	$75.35	$75.40
Purchase #2	$56.48	9.412%	$61.7959	$61.80	$61.80	$61.80
Purchase #3	$12.67	6.386%	$13.4791	$13.48	$13.50	$13.50
Purchase #4	$126.70	3.587%	$131.2447	$131.24	$131.25	$131.20
Purchase #5	$68.27	6.252%	$72.5382	$72.54	$72.55	$72.50
Purchase #6	$89.43	7.681%	$96.2991	$96.30	$96.30	$96.30
Purchase #7	$225.94	8.245%	$244.5688	$244.57	$244.55	$244.60
7 purchase totals =	$647.03		$695.2836	$695.29	$695.30	$695.30