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	$145.54	5.468%	$153.4981	$153.50	$153.50	$153.50
Purchase #2	$48.84	6.241%	$51.8881	$51.89	$51.90	$51.90
Purchase #3	$21.92	8.740%	$23.8358	$23.84	$23.85	$23.80
Purchase #4	$53.42	11.498%	$59.5622	$59.56	$59.55	$59.60
Purchase #5	$67.45	5.188%	$70.9493	$70.95	$70.95	$70.90
Purchase #6	$109.90	11.367%	$122.3923	$122.39	$122.40	$122.40
Purchase #7	$73.70	8.759%	$80.1554	$80.16	$80.15	$80.20
7 purchase totals =	$520.77		$562.2812	$562.29	$562.30	$562.30