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	$167.81	13.836%	$191.0282	$191.03	$191.05	$191.00
Purchase #2	$133.28	11.166%	$148.162	$148.16	$148.15	$148.20
Purchase #3	$83.89	12.635%	$94.4895	$94.49	$94.50	$94.50
Purchase #4	$69.49	9.715%	$76.241	$76.24	$76.25	$76.20
Purchase #5	$93.65	12.199%	$105.0744	$105.07	$105.05	$105.10
Purchase #6	$77.59	7.149%	$83.1369	$83.14	$83.15	$83.10
Purchase #7	$40.76	11.107%	$45.2872	$45.29	$45.30	$45.30
7 purchase totals =	$666.47		$743.4192	$743.42	$743.45	$743.40