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	$192.62	3.609%	$199.5717	$199.57	$199.55	$199.60
Purchase #2	$244.81	12.513%	$275.4431	$275.44	$275.45	$275.40
Purchase #3	$44.77	6.766%	$47.7991	$47.80	$47.80	$47.80
Purchase #4	$33.40	11.781%	$37.3349	$37.33	$37.35	$37.30
Purchase #5	$66.80	8.722%	$72.6263	$72.63	$72.65	$72.60
Purchase #6	$73.37	13.364%	$83.1752	$83.18	$83.20	$83.20
Purchase #7	$191.80	9.809%	$210.6137	$210.61	$210.60	$210.60
7 purchase totals =	$847.57		$926.5640	$926.56	$926.60	$926.50