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	$122.52	3.767%	$127.1353	$127.14	$127.15	$127.10
Purchase #2	$200.97	13.189%	$227.4759	$227.48	$227.50	$227.50
Purchase #3	$99.72	6.104%	$105.8069	$105.81	$105.80	$105.80
Purchase #4	$170.44	6.865%	$182.1407	$182.14	$182.15	$182.10
Purchase #5	$75.49	10.447%	$83.3764	$83.38	$83.40	$83.40
Purchase #6	$225.47	8.121%	$243.7804	$243.78	$243.80	$243.80
Purchase #7	$246.42	5.158%	$259.1303	$259.13	$259.15	$259.10
7 purchase totals =	$1,141.03		$1,228.8459	$1,228.86	$1,228.95	$1,228.80