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	$70.86	9.516%	$77.603	$77.60	$77.60	$77.60
Purchase #2	$60.61	3.241%	$62.5744	$62.57	$62.55	$62.60
Purchase #3	$78.59	3.142%	$81.0593	$81.06	$81.05	$81.10
Purchase #4	$185.69	13.457%	$210.6783	$210.68	$210.70	$210.70
Purchase #5	$222.94	7.816%	$240.365	$240.37	$240.35	$240.40
Purchase #6	$56.42	13.685%	$64.1411	$64.14	$64.15	$64.10
Purchase #7	$133.70	4.408%	$139.5935	$139.59	$139.60	$139.60
7 purchase totals =	$808.81		$876.0146	$876.01	$876.00	$876.10