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	$103.77	7.263%	$111.3068	$111.31	$111.30	$111.30
Purchase #2	$70.66	11.250%	$78.6093	$78.61	$78.60	$78.60
Purchase #3	$229.80	13.670%	$261.2137	$261.21	$261.20	$261.20
Purchase #4	$87.90	10.429%	$97.0671	$97.07	$97.05	$97.10
Purchase #5	$96.60	4.860%	$101.2948	$101.29	$101.30	$101.30
Purchase #6	$243.90	5.827%	$258.1121	$258.11	$258.10	$258.10
Purchase #7	$125.74	12.286%	$141.1884	$141.19	$141.20	$141.20
7 purchase totals =	$958.37		$1,048.7922	$1,048.79	$1,048.75	$1,048.80