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	$225.52	9.632%	$247.2421	$247.24	$247.25	$247.20
Purchase #2	$82.96	11.633%	$92.6107	$92.61	$92.60	$92.60
Purchase #3	$33.38	13.460%	$37.8729	$37.87	$37.85	$37.90
Purchase #4	$186.56	13.671%	$212.0646	$212.06	$212.05	$212.10
Purchase #5	$92.98	3.305%	$96.053	$96.05	$96.05	$96.10
Purchase #6	$250.30	9.784%	$274.7894	$274.79	$274.80	$274.80
Purchase #7	$130.75	5.249%	$137.6131	$137.61	$137.60	$137.60
7 purchase totals =	$1,002.45		$1,098.2458	$1,098.23	$1,098.20	$1,098.30