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	$204.80	8.783%	$222.7876	$222.79	$222.80	$222.80
Purchase #2	$234.31	3.114%	$241.6064	$241.61	$241.60	$241.60
Purchase #3	$37.61	11.363%	$41.8836	$41.88	$41.90	$41.90
Purchase #4	$168.25	13.323%	$190.6659	$190.67	$190.65	$190.70
Purchase #5	$116.53	10.320%	$128.5559	$128.56	$128.55	$128.60
Purchase #6	$41.36	7.232%	$44.3512	$44.35	$44.35	$44.40
Purchase #7	$250.57	13.576%	$284.5874	$284.59	$284.60	$284.60
7 purchase totals =	$1,053.43		$1,154.4380	$1,154.45	$1,154.45	$1,154.60