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	$40.92	13.430%	$46.4156	$46.42	$46.40	$46.40
Purchase #2	$154.96	6.524%	$165.0696	$165.07	$165.05	$165.10
Purchase #3	$132.36	8.348%	$143.4094	$143.41	$143.40	$143.40
Purchase #4	$138.31	7.190%	$148.2545	$148.25	$148.25	$148.30
Purchase #5	$224.48	13.155%	$254.0103	$254.01	$254.00	$254.00
Purchase #6	$98.59	6.806%	$105.3	$105.30	$105.30	$105.30
Purchase #7	$190.79	9.632%	$209.1669	$209.17	$209.15	$209.20
7 purchase totals =	$980.41		$1,071.6263	$1,071.63	$1,071.55	$1,071.70