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	$132.75	9.838%	$145.8099	$145.81	$145.80	$145.80
Purchase #2	$9.98	3.268%	$10.3061	$10.31	$10.30	$10.30
Purchase #3	$223.47	13.237%	$253.0507	$253.05	$253.05	$253.10
Purchase #4	$162.34	4.299%	$169.319	$169.32	$169.30	$169.30
Purchase #5	$6.79	10.367%	$7.4939	$7.49	$7.50	$7.50
Purchase #6	$225.92	5.483%	$238.3072	$238.31	$238.30	$238.30
Purchase #7	$240.70	13.363%	$272.8647	$272.86	$272.85	$272.90
7 purchase totals =	$1,001.95		$1,097.1515	$1,097.15	$1,097.10	$1,097.20