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	$43.66	5.130%	$45.8998	$45.90	$45.90	$45.90
Purchase #2	$165.29	3.331%	$170.7958	$170.80	$170.80	$170.80
Purchase #3	$127.71	9.629%	$140.0072	$140.01	$140.00	$140.00
Purchase #4	$108.57	3.868%	$112.7695	$112.77	$112.75	$112.80
Purchase #5	$244.42	12.824%	$275.7644	$275.76	$275.75	$275.80
Purchase #6	$246.25	11.204%	$273.8399	$273.84	$273.85	$273.80
Purchase #7	$169.43	9.544%	$185.6004	$185.60	$185.60	$185.60
7 purchase totals =	$1,105.33		$1,204.6770	$1,204.68	$1,204.65	$1,204.70