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	$208.82	3.222%	$215.5482	$215.55	$215.55	$215.50
Purchase #2	$71.46	5.721%	$75.5482	$75.55	$75.55	$75.50
Purchase #3	$172.73	3.313%	$178.4525	$178.45	$178.45	$178.50
Purchase #4	$115.97	8.228%	$125.512	$125.51	$125.50	$125.50
Purchase #5	$74.78	4.823%	$78.3866	$78.39	$78.40	$78.40
Purchase #6	$134.38	12.207%	$150.7838	$150.78	$150.80	$150.80
Purchase #7	$25.36	11.673%	$28.3203	$28.32	$28.30	$28.30
7 purchase totals =	$803.50		$852.5516	$852.55	$852.55	$852.50