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	$40.79	11.404%	$45.4417	$45.44	$45.45	$45.40
Purchase #2	$244.62	3.282%	$252.6484	$252.65	$252.65	$252.60
Purchase #3	$94.45	5.213%	$99.3737	$99.37	$99.35	$99.40
Purchase #4	$9.34	12.787%	$10.5343	$10.53	$10.55	$10.50
Purchase #5	$45.42	3.761%	$47.1282	$47.13	$47.15	$47.10
Purchase #6	$193.69	7.806%	$208.8094	$208.81	$208.80	$208.80
Purchase #7	$123.57	6.242%	$131.2832	$131.28	$131.30	$131.30
7 purchase totals =	$751.88		$795.2189	$795.21	$795.25	$795.10