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	$30.50	7.130%	$32.6747	$32.67	$32.65	$32.70
Purchase #2	$58.98	13.361%	$66.8603	$66.86	$66.85	$66.90
Purchase #3	$78.94	13.511%	$89.6056	$89.61	$89.60	$89.60
Purchase #4	$191.28	4.795%	$200.4519	$200.45	$200.45	$200.50
Purchase #5	$152.36	12.687%	$171.6899	$171.69	$171.70	$171.70
Purchase #6	$160.29	11.486%	$178.7009	$178.70	$178.70	$178.70
Purchase #7	$187.50	5.148%	$197.1525	$197.15	$197.15	$197.20
7 purchase totals =	$859.85		$937.1358	$937.13	$937.10	$937.30