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	$139.72	13.441%	$158.4998	$158.50	$158.50	$158.50
Purchase #2	$209.62	7.383%	$225.0962	$225.10	$225.10	$225.10
Purchase #3	$109.63	11.378%	$122.1037	$122.10	$122.10	$122.10
Purchase #4	$165.70	6.385%	$176.2799	$176.28	$176.30	$176.30
Purchase #5	$171.67	10.867%	$190.3254	$190.33	$190.35	$190.30
Purchase #6	$141.28	7.431%	$151.7785	$151.78	$151.80	$151.80
Purchase #7	$135.89	11.365%	$151.3339	$151.33	$151.35	$151.30
7 purchase totals =	$1,073.51		$1,175.4174	$1,175.42	$1,175.50	$1,175.40