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	$61.81	12.114%	$69.2977	$69.30	$69.30	$69.30
Purchase #2	$37.34	11.825%	$41.7555	$41.76	$41.75	$41.80
Purchase #3	$131.89	10.650%	$145.9363	$145.94	$145.95	$145.90
Purchase #4	$31.66	10.646%	$35.0305	$35.03	$35.05	$35.00
Purchase #5	$166.42	3.787%	$172.7223	$172.72	$172.70	$172.70
Purchase #6	$221.37	5.649%	$233.8752	$233.88	$233.90	$233.90
Purchase #7	$116.36	6.516%	$123.942	$123.94	$123.95	$123.90
7 purchase totals =	$766.85		$822.5595	$822.57	$822.60	$822.50