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	$164.43	5.304%	$173.1514	$173.15	$173.15	$173.20
Purchase #2	$163.91	3.442%	$169.5518	$169.55	$169.55	$169.60
Purchase #3	$234.96	12.453%	$264.2196	$264.22	$264.20	$264.20
Purchase #4	$76.87	8.686%	$83.5469	$83.55	$83.55	$83.50
Purchase #5	$138.57	6.673%	$147.8168	$147.82	$147.80	$147.80
Purchase #6	$218.92	9.105%	$238.8527	$238.85	$238.85	$238.90
Purchase #7	$242.65	5.261%	$255.4158	$255.42	$255.40	$255.40
7 purchase totals =	$1,240.31		$1,332.5550	$1,332.56	$1,332.50	$1,332.60