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	$111.96	11.563%	$124.9059	$124.91	$124.90	$124.90
Purchase #2	$205.55	4.432%	$214.66	$214.66	$214.65	$214.70
Purchase #3	$53.53	11.118%	$59.4815	$59.48	$59.50	$59.50
Purchase #4	$159.40	5.825%	$168.6851	$168.69	$168.70	$168.70
Purchase #5	$222.93	12.547%	$250.901	$250.90	$250.90	$250.90
Purchase #6	$199.88	4.108%	$208.0911	$208.09	$208.10	$208.10
Purchase #7	$211.93	7.464%	$227.7485	$227.75	$227.75	$227.70
7 purchase totals =	$1,165.18		$1,254.4731	$1,254.48	$1,254.50	$1,254.50