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	$201.36	7.354%	$216.168	$216.17	$216.15	$216.20
Purchase #2	$53.52	4.290%	$55.816	$55.82	$55.80	$55.80
Purchase #3	$88.80	3.106%	$91.5581	$91.56	$91.55	$91.60
Purchase #4	$124.43	5.160%	$130.8506	$130.85	$130.85	$130.90
Purchase #5	$132.25	5.297%	$139.2553	$139.26	$139.25	$139.30
Purchase #6	$247.41	10.591%	$273.6132	$273.61	$273.60	$273.60
Purchase #7	$47.74	10.251%	$52.6338	$52.63	$52.65	$52.60
7 purchase totals =	$895.51		$959.8950	$959.90	$959.85	$960.00