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	$209.87	11.193%	$233.3607	$233.36	$233.35	$233.40
Purchase #2	$42.51	4.427%	$44.3919	$44.39	$44.40	$44.40
Purchase #3	$88.37	13.846%	$100.6057	$100.61	$100.60	$100.60
Purchase #4	$99.93	12.660%	$112.5811	$112.58	$112.60	$112.60
Purchase #5	$211.84	5.608%	$223.72	$223.72	$223.70	$223.70
Purchase #6	$129.63	10.645%	$143.4291	$143.43	$143.45	$143.40
Purchase #7	$80.34	7.602%	$86.4474	$86.45	$86.45	$86.40
7 purchase totals =	$862.49		$944.5359	$944.54	$944.55	$944.50