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	$46.93	13.831%	$53.4209	$53.42	$53.40	$53.40
Purchase #2	$169.82	5.703%	$179.5048	$179.50	$179.50	$179.50
Purchase #3	$179.95	6.501%	$191.6485	$191.65	$191.65	$191.60
Purchase #4	$95.40	13.848%	$108.611	$108.61	$108.60	$108.60
Purchase #5	$171.90	12.171%	$192.8219	$192.82	$192.80	$192.80
Purchase #6	$170.79	10.327%	$188.4275	$188.43	$188.45	$188.40
Purchase #7	$33.27	7.483%	$35.7596	$35.76	$35.75	$35.80
7 purchase totals =	$868.06		$950.1942	$950.19	$950.15	$950.10