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	$91.38	8.382%	$99.0395	$99.04	$99.05	$99.00
Purchase #2	$136.87	8.731%	$148.8201	$148.82	$148.80	$148.80
Purchase #3	$76.83	13.588%	$87.2697	$87.27	$87.25	$87.30
Purchase #4	$199.46	3.370%	$206.1818	$206.18	$206.20	$206.20
Purchase #5	$92.61	13.682%	$105.2809	$105.28	$105.30	$105.30
Purchase #6	$155.42	8.473%	$168.5887	$168.59	$168.60	$168.60
Purchase #7	$201.55	13.790%	$229.3437	$229.34	$229.35	$229.30
7 purchase totals =	$954.12		$1,044.5244	$1,044.52	$1,044.55	$1,044.50