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	$42.94	13.629%	$48.7923	$48.79	$48.80	$48.80
Purchase #2	$61.81	6.266%	$65.683	$65.68	$65.70	$65.70
Purchase #3	$123.55	3.283%	$127.6061	$127.61	$127.60	$127.60
Purchase #4	$236.88	11.195%	$263.3987	$263.40	$263.40	$263.40
Purchase #5	$206.51	9.220%	$225.5502	$225.55	$225.55	$225.60
Purchase #6	$40.57	6.460%	$43.1908	$43.19	$43.20	$43.20
Purchase #7	$45.33	10.855%	$50.2506	$50.25	$50.25	$50.30
7 purchase totals =	$757.59		$824.4717	$824.47	$824.50	$824.60