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	$12.75	12.137%	$14.2975	$14.30	$14.30	$14.30
Purchase #2	$98.42	6.215%	$104.5368	$104.54	$104.55	$104.50
Purchase #3	$70.74	9.791%	$77.6662	$77.67	$77.65	$77.70
Purchase #4	$55.42	6.724%	$59.1464	$59.15	$59.15	$59.10
Purchase #5	$91.86	13.284%	$104.0627	$104.06	$104.05	$104.10
Purchase #6	$185.75	7.314%	$199.3358	$199.34	$199.35	$199.30
Purchase #7	$33.33	7.284%	$35.7578	$35.76	$35.75	$35.80
7 purchase totals =	$548.27		$594.8032	$594.82	$594.80	$594.80