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	$20.49	8.105%	$22.1507	$22.15	$22.15	$22.20
Purchase #2	$66.97	11.202%	$74.472	$74.47	$74.45	$74.50
Purchase #3	$147.88	12.103%	$165.7779	$165.78	$165.80	$165.80
Purchase #4	$128.74	12.550%	$144.8969	$144.90	$144.90	$144.90
Purchase #5	$171.63	11.774%	$191.8377	$191.84	$191.85	$191.80
Purchase #6	$59.54	8.260%	$64.458	$64.46	$64.45	$64.50
Purchase #7	$184.32	8.800%	$200.5402	$200.54	$200.55	$200.50
7 purchase totals =	$779.57		$864.1334	$864.14	$864.15	$864.20