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	$67.46	7.402%	$72.4534	$72.45	$72.45	$72.50
Purchase #2	$25.46	11.267%	$28.3286	$28.33	$28.35	$28.30
Purchase #3	$234.85	5.556%	$247.8983	$247.90	$247.90	$247.90
Purchase #4	$39.37	8.536%	$42.7306	$42.73	$42.75	$42.70
Purchase #5	$246.72	6.660%	$263.1516	$263.15	$263.15	$263.20
Purchase #6	$139.41	4.457%	$145.6235	$145.62	$145.60	$145.60
Purchase #7	$175.49	4.470%	$183.3344	$183.33	$183.35	$183.30
7 purchase totals =	$928.76		$983.5204	$983.51	$983.55	$983.50