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	$53.38	11.417%	$59.4744	$59.47	$59.45	$59.50
Purchase #2	$38.86	9.844%	$42.6854	$42.69	$42.70	$42.70
Purchase #3	$30.81	11.113%	$34.2339	$34.23	$34.25	$34.20
Purchase #4	$231.69	4.423%	$241.9376	$241.94	$241.95	$241.90
Purchase #5	$157.55	4.398%	$164.479	$164.48	$164.50	$164.50
Purchase #6	$248.54	6.482%	$264.6504	$264.65	$264.65	$264.70
Purchase #7	$46.52	10.230%	$51.279	$51.28	$51.30	$51.30
7 purchase totals =	$807.35		$858.7397	$858.74	$858.80	$858.80