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	$125.76	3.679%	$130.3867	$130.39	$130.40	$130.40
Purchase #2	$48.71	6.210%	$51.7349	$51.73	$51.75	$51.70
Purchase #3	$69.73	12.239%	$78.2643	$78.26	$78.25	$78.30
Purchase #4	$212.44	4.654%	$222.327	$222.33	$222.35	$222.30
Purchase #5	$166.64	3.495%	$172.4641	$172.46	$172.45	$172.50
Purchase #6	$82.80	12.143%	$92.8544	$92.85	$92.85	$92.90
Purchase #7	$239.48	7.497%	$257.4338	$257.43	$257.45	$257.40
7 purchase totals =	$945.56		$1,005.4652	$1,005.45	$1,005.50	$1,005.50