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	$80.65	12.535%	$90.7595	$90.76	$90.75	$90.80
Purchase #2	$241.53	11.459%	$269.2069	$269.21	$269.20	$269.20
Purchase #3	$117.95	5.697%	$124.6696	$124.67	$124.65	$124.70
Purchase #4	$43.94	11.530%	$49.0063	$49.01	$49.00	$49.00
Purchase #5	$80.86	10.470%	$89.326	$89.33	$89.35	$89.30
Purchase #6	$244.76	3.444%	$253.1895	$253.19	$253.20	$253.20
Purchase #7	$149.70	12.372%	$168.2209	$168.22	$168.20	$168.20
7 purchase totals =	$959.39		$1,044.3787	$1,044.39	$1,044.35	$1,044.40