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	$179.26	10.776%	$198.5771	$198.58	$198.60	$198.60
Purchase #2	$43.44	12.353%	$48.8061	$48.81	$48.80	$48.80
Purchase #3	$37.56	11.209%	$41.7701	$41.77	$41.75	$41.80
Purchase #4	$36.56	3.297%	$37.7654	$37.77	$37.75	$37.80
Purchase #5	$161.71	13.261%	$183.1544	$183.15	$183.15	$183.20
Purchase #6	$225.60	7.406%	$242.3079	$242.31	$242.30	$242.30
Purchase #7	$92.75	8.410%	$100.5503	$100.55	$100.55	$100.60
7 purchase totals =	$776.88		$852.9313	$852.94	$852.90	$853.10