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	$65.62	9.331%	$71.743	$71.74	$71.75	$71.70
Purchase #2	$217.83	13.318%	$246.8406	$246.84	$246.85	$246.80
Purchase #3	$143.54	12.314%	$161.2155	$161.22	$161.20	$161.20
Purchase #4	$212.82	6.769%	$227.2258	$227.23	$227.25	$227.20
Purchase #5	$78.63	4.359%	$82.0575	$82.06	$82.05	$82.10
Purchase #6	$188.35	4.293%	$196.4359	$196.44	$196.45	$196.40
Purchase #7	$110.27	3.182%	$113.7788	$113.78	$113.80	$113.80
7 purchase totals =	$1,017.06		$1,099.2971	$1,099.31	$1,099.35	$1,099.20