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	$61.57	7.641%	$66.2746	$66.27	$66.25	$66.30
Purchase #2	$35.60	5.822%	$37.6726	$37.67	$37.65	$37.70
Purchase #3	$28.31	3.499%	$29.3006	$29.30	$29.30	$29.30
Purchase #4	$218.93	4.626%	$229.0577	$229.06	$229.05	$229.10
Purchase #5	$62.81	7.400%	$67.4579	$67.46	$67.45	$67.50
Purchase #6	$77.68	11.693%	$86.7631	$86.76	$86.75	$86.80
Purchase #7	$44.76	4.501%	$46.7746	$46.77	$46.75	$46.80
7 purchase totals =	$529.66		$563.3011	$563.29	$563.20	$563.50