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	$198.44	4.528%	$207.4254	$207.43	$207.45	$207.40
Purchase #2	$160.67	10.802%	$178.0256	$178.03	$178.05	$178.00
Purchase #3	$63.65	13.786%	$72.4248	$72.42	$72.40	$72.40
Purchase #4	$242.72	12.503%	$273.0673	$273.07	$273.05	$273.10
Purchase #5	$240.38	5.850%	$254.4422	$254.44	$254.45	$254.40
Purchase #6	$43.45	5.644%	$45.9023	$45.90	$45.90	$45.90
Purchase #7	$134.89	10.686%	$149.3043	$149.30	$149.30	$149.30
7 purchase totals =	$1,084.20		$1,180.5919	$1,180.59	$1,180.60	$1,180.50