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	$97.45	13.609%	$110.712	$110.71	$110.70	$110.70
Purchase #2	$89.41	5.746%	$94.5475	$94.55	$94.55	$94.50
Purchase #3	$188.32	13.348%	$213.457	$213.46	$213.45	$213.50
Purchase #4	$185.38	4.723%	$194.1355	$194.14	$194.15	$194.10
Purchase #5	$90.45	7.265%	$97.0212	$97.02	$97.00	$97.00
Purchase #6	$95.76	13.130%	$108.3333	$108.33	$108.35	$108.30
Purchase #7	$53.93	10.724%	$59.7135	$59.71	$59.70	$59.70
7 purchase totals =	$800.70		$877.9200	$877.92	$877.90	$877.80