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	$90.74	13.525%	$103.0126	$103.01	$103.00	$103.00
Purchase #2	$213.39	9.521%	$233.7069	$233.71	$233.70	$233.70
Purchase #3	$79.81	7.364%	$85.6872	$85.69	$85.70	$85.70
Purchase #4	$59.27	12.241%	$66.5252	$66.53	$66.55	$66.50
Purchase #5	$238.74	11.738%	$266.7633	$266.76	$266.75	$266.80
Purchase #6	$91.25	10.174%	$100.5338	$100.53	$100.55	$100.50
Purchase #7	$25.34	11.281%	$28.1986	$28.20	$28.20	$28.20
7 purchase totals =	$798.54		$884.4276	$884.43	$884.45	$884.40