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	$120.71	13.506%	$137.0131	$137.01	$137.00	$137.00
Purchase #2	$47.28	3.754%	$49.0549	$49.05	$49.05	$49.10
Purchase #3	$32.52	13.685%	$36.9704	$36.97	$36.95	$37.00
Purchase #4	$132.75	13.201%	$150.2743	$150.27	$150.25	$150.30
Purchase #5	$37.74	9.435%	$41.3008	$41.30	$41.30	$41.30
Purchase #6	$171.57	11.626%	$191.5167	$191.52	$191.50	$191.50
Purchase #7	$56.91	8.196%	$61.5743	$61.57	$61.55	$61.60
7 purchase totals =	$599.48		$667.7045	$667.69	$667.60	$667.80