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	$130.90	7.704%	$140.9845	$140.98	$141.00	$141.00
Purchase #2	$129.70	3.643%	$134.425	$134.43	$134.45	$134.40
Purchase #3	$161.39	3.503%	$167.0435	$167.04	$167.05	$167.00
Purchase #4	$12.78	11.430%	$14.2408	$14.24	$14.25	$14.20
Purchase #5	$55.47	7.615%	$59.694	$59.69	$59.70	$59.70
Purchase #6	$132.37	5.355%	$139.4584	$139.46	$139.45	$139.50
Purchase #7	$89.44	11.707%	$99.9107	$99.91	$99.90	$99.90
7 purchase totals =	$712.05		$755.7569	$755.75	$755.80	$755.70