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	$148.78	5.576%	$157.076	$157.08	$157.10	$157.10
Purchase #2	$51.39	6.829%	$54.8994	$54.90	$54.90	$54.90
Purchase #3	$19.53	3.151%	$20.1454	$20.15	$20.15	$20.10
Purchase #4	$40.33	8.514%	$43.7637	$43.76	$43.75	$43.80
Purchase #5	$242.82	10.250%	$267.7091	$267.71	$267.70	$267.70
Purchase #6	$126.85	8.312%	$137.3938	$137.39	$137.40	$137.40
Purchase #7	$204.97	10.218%	$225.9138	$225.91	$225.90	$225.90
7 purchase totals =	$834.67		$906.9012	$906.90	$906.90	$906.90