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	$211.83	4.816%	$222.0317	$222.03	$222.05	$222.00
Purchase #2	$236.56	9.785%	$259.7074	$259.71	$259.70	$259.70
Purchase #3	$58.79	13.404%	$66.6702	$66.67	$66.65	$66.70
Purchase #4	$170.57	6.437%	$181.5496	$181.55	$181.55	$181.50
Purchase #5	$66.27	9.276%	$72.4172	$72.42	$72.40	$72.40
Purchase #6	$194.98	12.322%	$219.0054	$219.01	$219.00	$219.00
Purchase #7	$194.87	11.525%	$217.3288	$217.33	$217.35	$217.30
7 purchase totals =	$1,133.87		$1,238.7103	$1,238.72	$1,238.70	$1,238.60