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	$93.76	7.219%	$100.5285	$100.53	$100.55	$100.50
Purchase #2	$98.45	11.266%	$109.5414	$109.54	$109.55	$109.50
Purchase #3	$17.80	7.258%	$19.0919	$19.09	$19.10	$19.10
Purchase #4	$33.67	12.248%	$37.7939	$37.79	$37.80	$37.80
Purchase #5	$239.36	11.249%	$266.2856	$266.29	$266.30	$266.30
Purchase #6	$202.86	9.741%	$222.6206	$222.62	$222.60	$222.60
Purchase #7	$137.26	3.688%	$142.3221	$142.32	$142.30	$142.30
7 purchase totals =	$823.16		$898.1840	$898.18	$898.20	$898.10