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	$211.89	7.818%	$228.4556	$228.46	$228.45	$228.50
Purchase #2	$234.54	11.337%	$261.1298	$261.13	$261.15	$261.10
Purchase #3	$40.83	3.229%	$42.1484	$42.15	$42.15	$42.10
Purchase #4	$6.77	4.703%	$7.0884	$7.09	$7.10	$7.10
Purchase #5	$65.53	11.370%	$72.9808	$72.98	$73.00	$73.00
Purchase #6	$77.87	13.872%	$88.6721	$88.67	$88.65	$88.70
Purchase #7	$101.93	4.434%	$106.4496	$106.45	$106.45	$106.40
7 purchase totals =	$739.36		$806.9247	$806.93	$806.95	$806.90