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	$17.26	11.359%	$19.2206	$19.22	$19.20	$19.20
Purchase #2	$38.48	11.266%	$42.8152	$42.82	$42.80	$42.80
Purchase #3	$69.63	6.721%	$74.3098	$74.31	$74.30	$74.30
Purchase #4	$20.47	6.605%	$21.822	$21.82	$21.80	$21.80
Purchase #5	$33.65	12.345%	$37.8041	$37.80	$37.80	$37.80
Purchase #6	$199.36	13.114%	$225.5041	$225.50	$225.50	$225.50
Purchase #7	$236.97	11.624%	$264.5154	$264.52	$264.50	$264.50
7 purchase totals =	$615.82		$685.9912	$685.99	$685.90	$685.90