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	$162.27	11.234%	$180.4994	$180.50	$180.50	$180.50
Purchase #2	$243.70	13.187%	$275.8367	$275.84	$275.85	$275.80
Purchase #3	$163.63	11.367%	$182.2298	$182.23	$182.25	$182.20
Purchase #4	$123.96	8.538%	$134.5437	$134.54	$134.55	$134.50
Purchase #5	$186.30	6.853%	$199.0671	$199.07	$199.05	$199.10
Purchase #6	$131.59	9.759%	$144.4319	$144.43	$144.45	$144.40
Purchase #7	$32.46	8.305%	$35.1558	$35.16	$35.15	$35.20
7 purchase totals =	$1,043.91		$1,151.7644	$1,151.77	$1,151.80	$1,151.70