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	$46.72	8.130%	$50.5183	$50.52	$50.50	$50.50
Purchase #2	$125.35	4.742%	$131.2941	$131.29	$131.30	$131.30
Purchase #3	$182.56	11.147%	$202.91	$202.91	$202.90	$202.90
Purchase #4	$6.97	13.149%	$7.8865	$7.89	$7.90	$7.90
Purchase #5	$177.85	10.612%	$196.7234	$196.72	$196.70	$196.70
Purchase #6	$181.79	10.358%	$200.6198	$200.62	$200.60	$200.60
Purchase #7	$56.96	11.244%	$63.3646	$63.36	$63.35	$63.40
7 purchase totals =	$778.20		$853.3167	$853.31	$853.25	$853.30