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	$31.75	8.321%	$34.3919	$34.39	$34.40	$34.40
Purchase #2	$149.99	8.334%	$162.4902	$162.49	$162.50	$162.50
Purchase #3	$53.78	8.108%	$58.1405	$58.14	$58.15	$58.10
Purchase #4	$198.37	7.328%	$212.9066	$212.91	$212.90	$212.90
Purchase #5	$104.45	6.816%	$111.5693	$111.57	$111.55	$111.60
Purchase #6	$104.73	7.283%	$112.3575	$112.36	$112.35	$112.40
Purchase #7	$113.76	8.248%	$123.1429	$123.14	$123.15	$123.10
7 purchase totals =	$756.83		$814.9989	$815.00	$815.00	$815.00