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	$233.56	6.501%	$248.7437	$248.74	$248.75	$248.70
Purchase #2	$220.32	12.143%	$247.0735	$247.07	$247.05	$247.10
Purchase #3	$69.86	3.865%	$72.5601	$72.56	$72.55	$72.60
Purchase #4	$32.82	13.223%	$37.1598	$37.16	$37.15	$37.20
Purchase #5	$138.94	8.266%	$150.4248	$150.42	$150.40	$150.40
Purchase #6	$101.98	12.695%	$114.9264	$114.93	$114.95	$114.90
Purchase #7	$65.35	8.216%	$70.7192	$70.72	$70.70	$70.70
7 purchase totals =	$862.83		$941.6075	$941.60	$941.55	$941.60