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	$209.94	6.638%	$223.8758	$223.88	$223.90	$223.90
Purchase #2	$219.87	13.760%	$250.1241	$250.12	$250.10	$250.10
Purchase #3	$93.40	13.161%	$105.6924	$105.69	$105.70	$105.70
Purchase #4	$101.53	11.582%	$113.2892	$113.29	$113.30	$113.30
Purchase #5	$87.34	13.282%	$98.9405	$98.94	$98.95	$98.90
Purchase #6	$142.97	5.244%	$150.4673	$150.47	$150.45	$150.50
Purchase #7	$149.35	3.742%	$154.9387	$154.94	$154.95	$154.90
7 purchase totals =	$1,004.40		$1,097.3280	$1,097.33	$1,097.35	$1,097.30