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	$140.65	10.483%	$155.3943	$155.39	$155.40	$155.40
Purchase #2	$15.92	3.724%	$16.5129	$16.51	$16.50	$16.50
Purchase #3	$150.38	12.475%	$169.1399	$169.14	$169.15	$169.10
Purchase #4	$199.57	6.300%	$212.1429	$212.14	$212.15	$212.10
Purchase #5	$131.81	3.464%	$136.3759	$136.38	$136.40	$136.40
Purchase #6	$147.69	3.682%	$153.1279	$153.13	$153.15	$153.10
Purchase #7	$223.71	6.775%	$238.8664	$238.87	$238.85	$238.90
7 purchase totals =	$1,009.73		$1,081.5602	$1,081.56	$1,081.60	$1,081.50