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	$114.50	12.578%	$128.9018	$128.90	$128.90	$128.90
Purchase #2	$203.71	6.466%	$216.8819	$216.88	$216.90	$216.90
Purchase #3	$144.72	9.444%	$158.3874	$158.39	$158.40	$158.40
Purchase #4	$161.55	6.578%	$172.1768	$172.18	$172.20	$172.20
Purchase #5	$96.87	4.827%	$101.5459	$101.55	$101.55	$101.50
Purchase #6	$9.65	11.358%	$10.746	$10.75	$10.75	$10.70
Purchase #7	$165.76	4.242%	$172.7915	$172.79	$172.80	$172.80
7 purchase totals =	$896.76		$961.4313	$961.44	$961.50	$961.40