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	$183.72	8.237%	$198.853	$198.85	$198.85	$198.90
Purchase #2	$166.89	13.369%	$189.2015	$189.20	$189.20	$189.20
Purchase #3	$80.47	11.125%	$89.4223	$89.42	$89.40	$89.40
Purchase #4	$180.67	7.283%	$193.8282	$193.83	$193.85	$193.80
Purchase #5	$7.30	6.681%	$7.7877	$7.79	$7.80	$7.80
Purchase #6	$103.73	7.295%	$111.2971	$111.30	$111.30	$111.30
Purchase #7	$153.89	8.503%	$166.9753	$166.98	$167.00	$167.00
7 purchase totals =	$876.67		$957.3651	$957.37	$957.40	$957.40