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	$112.79	9.609%	$123.628	$123.63	$123.65	$123.60
Purchase #2	$51.41	6.216%	$54.6056	$54.61	$54.60	$54.60
Purchase #3	$220.25	10.564%	$243.5172	$243.52	$243.50	$243.50
Purchase #4	$161.26	7.105%	$172.7175	$172.72	$172.70	$172.70
Purchase #5	$57.47	6.154%	$61.0067	$61.01	$61.00	$61.00
Purchase #6	$230.96	12.367%	$259.5228	$259.52	$259.50	$259.50
Purchase #7	$184.49	13.652%	$209.6766	$209.68	$209.70	$209.70
7 purchase totals =	$1,018.63		$1,124.6744	$1,124.69	$1,124.65	$1,124.60