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	$204.52	3.540%	$211.76	$211.76	$211.75	$211.80
Purchase #2	$247.90	6.411%	$263.7929	$263.79	$263.80	$263.80
Purchase #3	$64.77	11.539%	$72.2438	$72.24	$72.25	$72.20
Purchase #4	$39.39	5.249%	$41.4576	$41.46	$41.45	$41.50
Purchase #5	$85.40	7.263%	$91.6026	$91.60	$91.60	$91.60
Purchase #6	$32.86	11.193%	$36.538	$36.54	$36.55	$36.50
Purchase #7	$103.76	10.702%	$114.8644	$114.86	$114.85	$114.90
7 purchase totals =	$778.60		$832.2593	$832.25	$832.25	$832.30