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	$239.88	5.794%	$253.7786	$253.78	$253.80	$253.80
Purchase #2	$137.81	10.244%	$151.9273	$151.93	$151.95	$151.90
Purchase #3	$65.74	7.845%	$70.8973	$70.90	$70.90	$70.90
Purchase #4	$143.39	8.261%	$155.2354	$155.24	$155.25	$155.20
Purchase #5	$57.79	12.479%	$65.0016	$65.00	$65.00	$65.00
Purchase #6	$247.57	6.424%	$263.4739	$263.47	$263.45	$263.50
Purchase #7	$240.68	6.173%	$255.5372	$255.54	$255.55	$255.50
7 purchase totals =	$1,132.86		$1,215.8513	$1,215.86	$1,215.90	$1,215.80