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	$131.97	7.308%	$141.6144	$141.61	$141.60	$141.60
Purchase #2	$195.82	5.542%	$206.6723	$206.67	$206.65	$206.70
Purchase #3	$189.84	5.238%	$199.7838	$199.78	$199.80	$199.80
Purchase #4	$244.84	3.709%	$253.9211	$253.92	$253.90	$253.90
Purchase #5	$215.40	3.172%	$222.2325	$222.23	$222.25	$222.20
Purchase #6	$91.28	9.834%	$100.2565	$100.26	$100.25	$100.30
Purchase #7	$63.76	13.517%	$72.3784	$72.38	$72.40	$72.40
7 purchase totals =	$1,132.91		$1,196.8590	$1,196.85	$1,196.85	$1,196.90