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	$197.41	12.583%	$222.2501	$222.25	$222.25	$222.30
Purchase #2	$133.62	4.565%	$139.7198	$139.72	$139.70	$139.70
Purchase #3	$146.61	10.108%	$161.4293	$161.43	$161.45	$161.40
Purchase #4	$28.95	10.201%	$31.9032	$31.90	$31.90	$31.90
Purchase #5	$185.40	6.341%	$197.1562	$197.16	$197.15	$197.20
Purchase #6	$54.81	13.841%	$62.3963	$62.40	$62.40	$62.40
Purchase #7	$103.53	5.790%	$109.5244	$109.52	$109.50	$109.50
7 purchase totals =	$850.33		$924.3793	$924.38	$924.35	$924.40