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	$10.42	8.433%	$11.2987	$11.30	$11.30	$11.30
Purchase #2	$208.28	9.279%	$227.6063	$227.61	$227.60	$227.60
Purchase #3	$37.67	9.519%	$41.2558	$41.26	$41.25	$41.30
Purchase #4	$72.44	11.204%	$80.5562	$80.56	$80.55	$80.60
Purchase #5	$46.90	13.710%	$53.33	$53.33	$53.35	$53.30
Purchase #6	$125.95	11.576%	$140.53	$140.53	$140.55	$140.50
Purchase #7	$154.39	8.518%	$167.5409	$167.54	$167.55	$167.50
7 purchase totals =	$656.05		$722.1179	$722.13	$722.15	$722.10