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	$37.61	8.233%	$40.7064	$40.71	$40.70	$40.70
Purchase #2	$39.92	8.241%	$43.2098	$43.21	$43.20	$43.20
Purchase #3	$91.79	5.531%	$96.8669	$96.87	$96.85	$96.90
Purchase #4	$154.90	6.574%	$165.0831	$165.08	$165.10	$165.10
Purchase #5	$212.52	11.457%	$236.8684	$236.87	$236.85	$236.90
Purchase #6	$139.74	8.385%	$151.4572	$151.46	$151.45	$151.50
Purchase #7	$137.63	10.614%	$152.238	$152.24	$152.25	$152.20
7 purchase totals =	$814.11		$886.4298	$886.44	$886.40	$886.50