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	$184.43	5.336%	$194.2712	$194.27	$194.25	$194.30
Purchase #2	$112.59	6.240%	$119.6156	$119.62	$119.60	$119.60
Purchase #3	$183.27	13.566%	$208.1324	$208.13	$208.15	$208.10
Purchase #4	$61.39	13.294%	$69.5512	$69.55	$69.55	$69.60
Purchase #5	$80.96	6.814%	$86.4766	$86.48	$86.50	$86.50
Purchase #6	$148.53	6.279%	$157.8562	$157.86	$157.85	$157.90
Purchase #7	$59.73	13.300%	$67.6741	$67.67	$67.65	$67.70
7 purchase totals =	$830.90		$903.5773	$903.58	$903.55	$903.70