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	$180.25	9.563%	$197.4873	$197.49	$197.50	$197.50
Purchase #2	$79.25	13.437%	$89.8988	$89.90	$89.90	$89.90
Purchase #3	$86.32	13.592%	$98.0526	$98.05	$98.05	$98.10
Purchase #4	$87.54	11.726%	$97.8049	$97.80	$97.80	$97.80
Purchase #5	$28.30	13.448%	$32.1058	$32.11	$32.10	$32.10
Purchase #6	$99.51	5.478%	$104.9612	$104.96	$104.95	$105.00
Purchase #7	$117.77	11.838%	$131.7116	$131.71	$131.70	$131.70
7 purchase totals =	$678.94		$752.0222	$752.02	$752.00	$752.10