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	$74.39	10.300%	$82.0522	$82.05	$82.05	$82.10
Purchase #2	$213.60	4.223%	$222.6203	$222.62	$222.60	$222.60
Purchase #3	$23.74	3.751%	$24.6305	$24.63	$24.65	$24.60
Purchase #4	$194.45	8.381%	$210.7469	$210.75	$210.75	$210.70
Purchase #5	$90.71	4.426%	$94.7248	$94.72	$94.70	$94.70
Purchase #6	$137.70	9.547%	$150.8462	$150.85	$150.85	$150.80
Purchase #7	$108.27	5.760%	$114.5064	$114.51	$114.50	$114.50
7 purchase totals =	$842.86		$900.1273	$900.13	$900.10	$900.00