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	$232.50	8.507%	$252.2788	$252.28	$252.30	$252.30
Purchase #2	$101.52	12.585%	$114.2963	$114.30	$114.30	$114.30
Purchase #3	$117.41	11.637%	$131.073	$131.07	$131.05	$131.10
Purchase #4	$223.61	10.585%	$247.2791	$247.28	$247.30	$247.30
Purchase #5	$174.78	12.574%	$196.7568	$196.76	$196.75	$196.80
Purchase #6	$71.29	10.682%	$78.9052	$78.91	$78.90	$78.90
Purchase #7	$82.25	8.674%	$89.3844	$89.38	$89.40	$89.40
7 purchase totals =	$1,003.36		$1,109.9736	$1,109.98	$1,110.00	$1,110.10