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	$151.56	9.495%	$165.9506	$165.95	$165.95	$166.00
Purchase #2	$74.60	11.395%	$83.1007	$83.10	$83.10	$83.10
Purchase #3	$104.63	3.818%	$108.6248	$108.62	$108.60	$108.60
Purchase #4	$141.52	6.424%	$150.6112	$150.61	$150.60	$150.60
Purchase #5	$134.60	11.215%	$149.6954	$149.70	$149.70	$149.70
Purchase #6	$228.79	11.673%	$255.4967	$255.50	$255.50	$255.50
Purchase #7	$86.31	9.642%	$94.632	$94.63	$94.65	$94.60
7 purchase totals =	$922.01		$1,008.1114	$1,008.11	$1,008.10	$1,008.10