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	$187.31	9.146%	$204.4414	$204.44	$204.45	$204.40
Purchase #2	$39.51	7.330%	$42.4061	$42.41	$42.40	$42.40
Purchase #3	$217.57	12.539%	$244.8511	$244.85	$244.85	$244.90
Purchase #4	$230.39	12.747%	$259.7578	$259.76	$259.75	$259.80
Purchase #5	$40.81	10.312%	$45.0183	$45.02	$45.00	$45.00
Purchase #6	$212.56	12.124%	$238.3308	$238.33	$238.35	$238.30
Purchase #7	$134.63	4.316%	$140.4406	$140.44	$140.45	$140.40
7 purchase totals =	$1,062.78		$1,175.2461	$1,175.25	$1,175.25	$1,175.20