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	$106.68	10.638%	$118.0286	$118.03	$118.05	$118.00
Purchase #2	$123.69	7.188%	$132.5808	$132.58	$132.60	$132.60
Purchase #3	$215.42	13.191%	$243.8361	$243.84	$243.85	$243.80
Purchase #4	$190.32	5.385%	$200.5687	$200.57	$200.55	$200.60
Purchase #5	$39.30	5.104%	$41.3059	$41.31	$41.30	$41.30
Purchase #6	$128.37	11.519%	$143.1569	$143.16	$143.15	$143.20
Purchase #7	$43.61	8.620%	$47.3692	$47.37	$47.35	$47.40
7 purchase totals =	$847.39		$926.8462	$926.86	$926.85	$926.90