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	$133.97	9.869%	$147.1915	$147.19	$147.20	$147.20
Purchase #2	$89.66	12.511%	$100.8774	$100.88	$100.90	$100.90
Purchase #3	$44.57	4.313%	$46.4923	$46.49	$46.50	$46.50
Purchase #4	$190.98	13.275%	$216.3326	$216.33	$216.35	$216.30
Purchase #5	$67.78	3.598%	$70.2187	$70.22	$70.20	$70.20
Purchase #6	$27.80	12.313%	$31.223	$31.22	$31.20	$31.20
Purchase #7	$107.25	6.748%	$114.4872	$114.49	$114.50	$114.50
7 purchase totals =	$662.01		$726.8227	$726.82	$726.85	$726.80