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	$131.74	7.288%	$141.3412	$141.34	$141.35	$141.30
Purchase #2	$20.50	9.731%	$22.4949	$22.49	$22.50	$22.50
Purchase #3	$203.36	4.565%	$212.6434	$212.64	$212.65	$212.60
Purchase #4	$78.84	12.194%	$88.4537	$88.45	$88.45	$88.50
Purchase #5	$130.36	7.439%	$140.0575	$140.06	$140.05	$140.10
Purchase #6	$18.72	9.142%	$20.4314	$20.43	$20.45	$20.40
Purchase #7	$54.92	8.392%	$59.5289	$59.53	$59.55	$59.50
7 purchase totals =	$638.44		$684.9510	$684.94	$685.00	$684.90