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	$79.38	3.128%	$81.863	$81.86	$81.85	$81.90
Purchase #2	$171.30	5.244%	$180.283	$180.28	$180.30	$180.30
Purchase #3	$93.47	4.482%	$97.6593	$97.66	$97.65	$97.70
Purchase #4	$44.89	8.185%	$48.5642	$48.56	$48.55	$48.60
Purchase #5	$63.72	3.279%	$65.8094	$65.81	$65.80	$65.80
Purchase #6	$147.78	12.288%	$165.9392	$165.94	$165.95	$165.90
Purchase #7	$177.64	10.534%	$196.3526	$196.35	$196.35	$196.40
7 purchase totals =	$778.18		$836.4707	$836.46	$836.45	$836.60