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	$7.34	3.283%	$7.581	$7.58	$7.60	$7.60
Purchase #2	$182.94	7.373%	$196.4282	$196.43	$196.45	$196.40
Purchase #3	$182.88	3.232%	$188.7907	$188.79	$188.80	$188.80
Purchase #4	$40.76	3.248%	$42.0839	$42.08	$42.10	$42.10
Purchase #5	$27.43	6.700%	$29.2678	$29.27	$29.25	$29.30
Purchase #6	$206.86	10.462%	$228.5017	$228.50	$228.50	$228.50
Purchase #7	$168.87	13.544%	$191.7418	$191.74	$191.75	$191.70
7 purchase totals =	$817.08		$884.3951	$884.39	$884.45	$884.40