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	$92.42	12.427%	$103.905	$103.91	$103.90	$103.90
Purchase #2	$160.31	11.773%	$179.1833	$179.18	$179.20	$179.20
Purchase #3	$151.64	13.815%	$172.5891	$172.59	$172.60	$172.60
Purchase #4	$99.51	3.638%	$103.1302	$103.13	$103.15	$103.10
Purchase #5	$140.90	11.566%	$157.1965	$157.20	$157.20	$157.20
Purchase #6	$211.46	6.214%	$224.6001	$224.60	$224.60	$224.60
Purchase #7	$72.77	12.318%	$81.7338	$81.73	$81.75	$81.70
7 purchase totals =	$929.01		$1,022.3380	$1,022.34	$1,022.40	$1,022.30