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	$83.77	4.777%	$87.7717	$87.77	$87.75	$87.80
Purchase #2	$76.88	8.232%	$83.2088	$83.21	$83.20	$83.20
Purchase #3	$83.38	7.518%	$89.6485	$89.65	$89.65	$89.60
Purchase #4	$149.56	3.690%	$155.0788	$155.08	$155.10	$155.10
Purchase #5	$178.72	3.850%	$185.6007	$185.60	$185.60	$185.60
Purchase #6	$219.41	7.205%	$235.2185	$235.22	$235.20	$235.20
Purchase #7	$159.51	12.216%	$178.9957	$179.00	$179.00	$179.00
7 purchase totals =	$951.23		$1,015.5227	$1,015.53	$1,015.50	$1,015.50