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	$72.57	6.483%	$77.2747	$77.27	$77.25	$77.30
Purchase #2	$77.30	3.868%	$80.29	$80.29	$80.30	$80.30
Purchase #3	$193.55	13.746%	$220.1554	$220.16	$220.15	$220.20
Purchase #4	$142.98	12.216%	$160.4464	$160.45	$160.45	$160.40
Purchase #5	$139.66	6.364%	$148.548	$148.55	$148.55	$148.50
Purchase #6	$99.65	11.591%	$111.2004	$111.20	$111.20	$111.20
Purchase #7	$137.73	13.635%	$156.5095	$156.51	$156.50	$156.50
7 purchase totals =	$863.44		$954.4244	$954.43	$954.40	$954.40