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	$95.80	8.260%	$103.7131	$103.71	$103.70	$103.70
Purchase #2	$71.92	3.270%	$74.2718	$74.27	$74.25	$74.30
Purchase #3	$118.54	11.179%	$131.7916	$131.79	$131.80	$131.80
Purchase #4	$144.26	3.534%	$149.3581	$149.36	$149.35	$149.40
Purchase #5	$119.28	3.492%	$123.4453	$123.45	$123.45	$123.40
Purchase #6	$118.62	8.310%	$128.4773	$128.48	$128.50	$128.50
Purchase #7	$241.83	7.442%	$259.827	$259.83	$259.85	$259.80
7 purchase totals =	$910.25		$970.8842	$970.89	$970.90	$970.90