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	$85.64	13.159%	$96.9094	$96.91	$96.90	$96.90
Purchase #2	$116.92	4.502%	$122.1837	$122.18	$122.20	$122.20
Purchase #3	$42.51	11.801%	$47.5266	$47.53	$47.55	$47.50
Purchase #4	$50.61	7.838%	$54.5768	$54.58	$54.60	$54.60
Purchase #5	$109.96	10.665%	$121.6872	$121.69	$121.70	$121.70
Purchase #6	$82.64	4.862%	$86.658	$86.66	$86.65	$86.70
Purchase #7	$41.49	3.406%	$42.9031	$42.90	$42.90	$42.90
7 purchase totals =	$529.77		$572.4448	$572.45	$572.50	$572.50