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	$85.54	10.408%	$94.443	$94.44	$94.45	$94.40
Purchase #2	$213.34	11.672%	$238.241	$238.24	$238.25	$238.20
Purchase #3	$77.91	5.717%	$82.3641	$82.36	$82.35	$82.40
Purchase #4	$72.37	13.457%	$82.1088	$82.11	$82.10	$82.10
Purchase #5	$42.89	13.528%	$48.6922	$48.69	$48.70	$48.70
Purchase #6	$94.38	11.211%	$104.9609	$104.96	$104.95	$105.00
Purchase #7	$184.25	5.314%	$194.041	$194.04	$194.05	$194.00
7 purchase totals =	$770.68		$844.8510	$844.84	$844.85	$844.80