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	$53.46	9.423%	$58.4975	$58.50	$58.50	$58.50
Purchase #2	$85.99	6.723%	$91.7711	$91.77	$91.75	$91.80
Purchase #3	$191.60	4.810%	$200.816	$200.82	$200.80	$200.80
Purchase #4	$167.86	3.604%	$173.9097	$173.91	$173.90	$173.90
Purchase #5	$195.35	10.317%	$215.5043	$215.50	$215.50	$215.50
Purchase #6	$54.93	12.235%	$61.6507	$61.65	$61.65	$61.70
Purchase #7	$95.57	9.450%	$104.6014	$104.60	$104.60	$104.60
7 purchase totals =	$844.76		$906.7507	$906.75	$906.70	$906.80