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	$223.62	3.758%	$232.0236	$232.02	$232.00	$232.00
Purchase #2	$115.30	11.455%	$128.5076	$128.51	$128.50	$128.50
Purchase #3	$71.50	9.308%	$78.1552	$78.16	$78.15	$78.20
Purchase #4	$85.56	9.441%	$93.6377	$93.64	$93.65	$93.60
Purchase #5	$193.70	8.268%	$209.7151	$209.72	$209.70	$209.70
Purchase #6	$160.86	12.755%	$181.3777	$181.38	$181.40	$181.40
Purchase #7	$53.83	10.658%	$59.5672	$59.57	$59.55	$59.60
7 purchase totals =	$904.37		$982.9841	$983.00	$982.95	$983.00