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	$104.83	7.334%	$112.5182	$112.52	$112.50	$112.50
Purchase #2	$79.77	12.551%	$89.7819	$89.78	$89.80	$89.80
Purchase #3	$85.71	6.374%	$91.1732	$91.17	$91.15	$91.20
Purchase #4	$45.34	12.113%	$50.832	$50.83	$50.85	$50.80
Purchase #5	$95.50	7.337%	$102.5068	$102.51	$102.50	$102.50
Purchase #6	$199.43	7.487%	$214.3613	$214.36	$214.35	$214.40
Purchase #7	$227.38	7.207%	$243.7673	$243.77	$243.75	$243.80
7 purchase totals =	$837.96		$904.9407	$904.94	$904.90	$905.00