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	$64.27	9.720%	$70.517	$70.52	$70.50	$70.50
Purchase #2	$236.84	9.510%	$259.3635	$259.36	$259.35	$259.40
Purchase #3	$203.56	9.654%	$223.2117	$223.21	$223.20	$223.20
Purchase #4	$152.95	7.478%	$164.3876	$164.39	$164.40	$164.40
Purchase #5	$10.55	3.630%	$10.933	$10.93	$10.95	$10.90
Purchase #6	$81.28	11.673%	$90.7678	$90.77	$90.75	$90.80
Purchase #7	$6.90	8.835%	$7.5096	$7.51	$7.50	$7.50
7 purchase totals =	$756.35		$826.6902	$826.69	$826.65	$826.70