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	$193.51	9.786%	$212.4469	$212.45	$212.45	$212.40
Purchase #2	$180.80	8.850%	$196.8008	$196.80	$196.80	$196.80
Purchase #3	$234.98	7.495%	$252.5918	$252.59	$252.60	$252.60
Purchase #4	$122.89	3.780%	$127.5352	$127.54	$127.55	$127.50
Purchase #5	$25.70	10.312%	$28.3502	$28.35	$28.35	$28.40
Purchase #6	$144.60	9.196%	$157.8974	$157.90	$157.90	$157.90
Purchase #7	$157.98	11.157%	$175.6058	$175.61	$175.60	$175.60
7 purchase totals =	$1,060.46		$1,151.2281	$1,151.24	$1,151.25	$1,151.20