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	$95.81	4.608%	$100.2249	$100.22	$100.20	$100.20
Purchase #2	$226.88	10.863%	$251.526	$251.53	$251.55	$251.50
Purchase #3	$23.39	12.515%	$26.3173	$26.32	$26.30	$26.30
Purchase #4	$185.50	6.105%	$196.8248	$196.82	$196.80	$196.80
Purchase #5	$168.53	4.731%	$176.5032	$176.50	$176.50	$176.50
Purchase #6	$30.73	8.253%	$33.2661	$33.27	$33.25	$33.30
Purchase #7	$194.46	3.162%	$200.6088	$200.61	$200.60	$200.60
7 purchase totals =	$925.30		$985.2711	$985.27	$985.20	$985.20