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	$210.83	3.751%	$218.7382	$218.74	$218.75	$218.70
Purchase #2	$75.45	4.498%	$78.8437	$78.84	$78.85	$78.80
Purchase #3	$99.30	13.325%	$112.5317	$112.53	$112.55	$112.50
Purchase #4	$118.27	13.819%	$134.6137	$134.61	$134.60	$134.60
Purchase #5	$185.60	13.796%	$211.2054	$211.21	$211.20	$211.20
Purchase #6	$19.53	13.583%	$22.1828	$22.18	$22.20	$22.20
Purchase #7	$243.67	12.130%	$273.2272	$273.23	$273.25	$273.20
7 purchase totals =	$952.65		$1,051.3427	$1,051.34	$1,051.40	$1,051.20