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	$31.81	4.282%	$33.1721	$33.17	$33.15	$33.20
Purchase #2	$69.30	13.471%	$78.6354	$78.64	$78.65	$78.60
Purchase #3	$242.93	4.355%	$253.5096	$253.51	$253.50	$253.50
Purchase #4	$151.76	4.632%	$158.7895	$158.79	$158.80	$158.80
Purchase #5	$246.27	10.343%	$271.7417	$271.74	$271.75	$271.70
Purchase #6	$171.65	8.621%	$186.4479	$186.45	$186.45	$186.40
Purchase #7	$26.48	7.698%	$28.5184	$28.52	$28.50	$28.50
7 purchase totals =	$940.20		$1,010.8146	$1,010.82	$1,010.80	$1,010.70