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	$16.75	5.715%	$17.7073	$17.71	$17.70	$17.70
Purchase #2	$35.76	5.117%	$37.5898	$37.59	$37.60	$37.60
Purchase #3	$241.72	9.268%	$264.1226	$264.12	$264.10	$264.10
Purchase #4	$31.40	6.690%	$33.5007	$33.50	$33.50	$33.50
Purchase #5	$188.56	13.671%	$214.338	$214.34	$214.35	$214.30
Purchase #6	$40.32	13.647%	$45.8225	$45.82	$45.80	$45.80
Purchase #7	$100.60	3.700%	$104.3222	$104.32	$104.30	$104.30
7 purchase totals =	$655.11		$717.4031	$717.40	$717.35	$717.30