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	$219.68	7.332%	$235.7869	$235.79	$235.80	$235.80
Purchase #2	$124.46	13.173%	$140.8551	$140.86	$140.85	$140.90
Purchase #3	$102.41	8.849%	$111.4723	$111.47	$111.45	$111.50
Purchase #4	$174.32	6.473%	$185.6037	$185.60	$185.60	$185.60
Purchase #5	$50.49	8.826%	$54.9462	$54.95	$54.95	$54.90
Purchase #6	$61.38	8.716%	$66.7299	$66.73	$66.75	$66.70
Purchase #7	$106.55	7.441%	$114.4784	$114.48	$114.50	$114.50
7 purchase totals =	$839.29		$909.8725	$909.88	$909.90	$909.90