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	$96.57	13.508%	$109.6147	$109.61	$109.60	$109.60
Purchase #2	$5.33	12.143%	$5.9772	$5.98	$6.00	$6.00
Purchase #3	$83.91	8.616%	$91.1397	$91.14	$91.15	$91.10
Purchase #4	$20.46	3.123%	$21.099	$21.10	$21.10	$21.10
Purchase #5	$76.58	11.162%	$85.1279	$85.13	$85.15	$85.10
Purchase #6	$134.65	8.688%	$146.3484	$146.35	$146.35	$146.30
Purchase #7	$37.81	9.245%	$41.3055	$41.31	$41.30	$41.30
7 purchase totals =	$455.31		$500.6124	$500.62	$500.65	$500.50