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	$131.48	4.774%	$137.7569	$137.76	$137.75	$137.80
Purchase #2	$91.60	6.286%	$97.358	$97.36	$97.35	$97.40
Purchase #3	$105.76	4.483%	$110.5012	$110.50	$110.50	$110.50
Purchase #4	$60.64	8.339%	$65.6968	$65.70	$65.70	$65.70
Purchase #5	$35.56	5.782%	$37.6161	$37.62	$37.60	$37.60
Purchase #6	$65.35	10.723%	$72.3575	$72.36	$72.35	$72.40
Purchase #7	$45.82	11.674%	$51.169	$51.17	$51.15	$51.20
7 purchase totals =	$536.21		$572.4555	$572.47	$572.40	$572.60