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	$129.68	11.715%	$144.872	$144.87	$144.85	$144.90
Purchase #2	$42.77	13.564%	$48.5713	$48.57	$48.55	$48.60
Purchase #3	$112.67	13.414%	$127.7836	$127.78	$127.80	$127.80
Purchase #4	$186.38	11.764%	$208.3057	$208.31	$208.30	$208.30
Purchase #5	$129.78	6.261%	$137.9055	$137.91	$137.90	$137.90
Purchase #6	$157.56	10.601%	$174.2629	$174.26	$174.25	$174.30
Purchase #7	$18.86	12.235%	$21.1675	$21.17	$21.15	$21.20
7 purchase totals =	$777.70		$862.8685	$862.87	$862.80	$863.00