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	$120.91	9.159%	$131.9841	$131.98	$132.00	$132.00
Purchase #2	$70.63	11.323%	$78.6274	$78.63	$78.65	$78.60
Purchase #3	$137.75	7.232%	$147.7121	$147.71	$147.70	$147.70
Purchase #4	$135.68	10.428%	$149.8287	$149.83	$149.85	$149.80
Purchase #5	$105.97	5.551%	$111.8524	$111.85	$111.85	$111.90
Purchase #6	$130.25	10.758%	$144.2623	$144.26	$144.25	$144.30
Purchase #7	$75.32	9.576%	$82.5326	$82.53	$82.55	$82.50
7 purchase totals =	$776.51		$846.7996	$846.79	$846.85	$846.80