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	$127.48	4.830%	$133.6373	$133.64	$133.65	$133.60
Purchase #2	$135.86	5.335%	$143.1081	$143.11	$143.10	$143.10
Purchase #3	$216.34	8.515%	$234.7614	$234.76	$234.75	$234.80
Purchase #4	$101.57	11.618%	$113.3704	$113.37	$113.35	$113.40
Purchase #5	$215.39	3.679%	$223.3142	$223.31	$223.30	$223.30
Purchase #6	$12.92	12.315%	$14.5111	$14.51	$14.50	$14.50
Purchase #7	$78.67	13.601%	$89.3699	$89.37	$89.35	$89.40
7 purchase totals =	$888.23		$952.0724	$952.07	$952.00	$952.10