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	$180.98	6.412%	$192.5844	$192.58	$192.60	$192.60
Purchase #2	$70.88	12.623%	$79.8272	$79.83	$79.85	$79.80
Purchase #3	$234.67	6.865%	$250.7801	$250.78	$250.80	$250.80
Purchase #4	$117.45	6.544%	$125.1359	$125.14	$125.15	$125.10
Purchase #5	$88.94	12.316%	$99.8939	$99.89	$99.90	$99.90
Purchase #6	$53.89	10.846%	$59.7349	$59.73	$59.75	$59.70
Purchase #7	$55.68	7.389%	$59.7942	$59.79	$59.80	$59.80
7 purchase totals =	$802.49		$867.7506	$867.74	$867.85	$867.70