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	$44.47	7.119%	$47.6358	$47.64	$47.65	$47.60
Purchase #2	$52.91	12.679%	$59.6185	$59.62	$59.60	$59.60
Purchase #3	$142.68	7.143%	$152.8716	$152.87	$152.85	$152.90
Purchase #4	$26.80	13.431%	$30.3995	$30.40	$30.40	$30.40
Purchase #5	$91.67	11.607%	$102.3101	$102.31	$102.30	$102.30
Purchase #6	$35.39	4.549%	$36.9999	$37.00	$37.00	$37.00
Purchase #7	$136.98	5.611%	$144.6659	$144.67	$144.65	$144.70
7 purchase totals =	$530.90		$574.5013	$574.51	$574.45	$574.50