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	$132.92	9.317%	$145.3042	$145.30	$145.30	$145.30
Purchase #2	$17.85	8.745%	$19.411	$19.41	$19.40	$19.40
Purchase #3	$62.87	13.165%	$71.1468	$71.15	$71.15	$71.10
Purchase #4	$95.34	10.726%	$105.5662	$105.57	$105.55	$105.60
Purchase #5	$184.91	8.543%	$200.7069	$200.71	$200.70	$200.70
Purchase #6	$67.90	12.392%	$76.3142	$76.31	$76.30	$76.30
Purchase #7	$146.58	10.872%	$162.5162	$162.52	$162.50	$162.50
7 purchase totals =	$708.37		$780.9655	$780.97	$780.90	$780.90