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	$78.53	8.447%	$85.1634	$85.16	$85.15	$85.20
Purchase #2	$103.79	12.375%	$116.634	$116.63	$116.65	$116.60
Purchase #3	$62.88	3.538%	$65.1047	$65.10	$65.10	$65.10
Purchase #4	$168.26	12.540%	$189.3598	$189.36	$189.35	$189.40
Purchase #5	$84.84	5.335%	$89.3662	$89.37	$89.35	$89.40
Purchase #6	$61.90	7.469%	$66.5233	$66.52	$66.50	$66.50
Purchase #7	$196.26	3.760%	$203.6394	$203.64	$203.65	$203.60
7 purchase totals =	$756.46		$815.7908	$815.78	$815.75	$815.80