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	$137.66	7.476%	$147.9515	$147.95	$147.95	$148.00
Purchase #2	$62.43	7.641%	$67.2003	$67.20	$67.20	$67.20
Purchase #3	$148.73	3.197%	$153.4849	$153.48	$153.50	$153.50
Purchase #4	$38.98	9.588%	$42.7174	$42.72	$42.70	$42.70
Purchase #5	$243.43	9.340%	$266.1664	$266.17	$266.15	$266.20
Purchase #6	$103.50	5.758%	$109.4595	$109.46	$109.45	$109.50
Purchase #7	$177.78	4.211%	$185.2663	$185.27	$185.25	$185.30
7 purchase totals =	$912.51		$972.2463	$972.25	$972.20	$972.40