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	$43.29	6.794%	$46.2311	$46.23	$46.25	$46.20
Purchase #2	$81.45	9.388%	$89.0965	$89.10	$89.10	$89.10
Purchase #3	$244.29	8.282%	$264.5221	$264.52	$264.50	$264.50
Purchase #4	$107.97	3.558%	$111.8116	$111.81	$111.80	$111.80
Purchase #5	$182.50	5.582%	$192.6872	$192.69	$192.70	$192.70
Purchase #6	$153.49	9.821%	$168.5643	$168.56	$168.55	$168.60
Purchase #7	$140.56	4.496%	$146.8796	$146.88	$146.90	$146.90
7 purchase totals =	$953.55		$1,019.7924	$1,019.79	$1,019.80	$1,019.80