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	$85.71	6.600%	$91.3669	$91.37	$91.35	$91.40
Purchase #2	$230.93	4.688%	$241.756	$241.76	$241.75	$241.80
Purchase #3	$102.30	3.156%	$105.5286	$105.53	$105.55	$105.50
Purchase #4	$188.43	4.507%	$196.9225	$196.92	$196.90	$196.90
Purchase #5	$32.98	3.112%	$34.0063	$34.01	$34.00	$34.00
Purchase #6	$200.96	3.855%	$208.707	$208.71	$208.70	$208.70
Purchase #7	$132.39	10.588%	$146.4075	$146.41	$146.40	$146.40
7 purchase totals =	$973.70		$1,024.6948	$1,024.71	$1,024.65	$1,024.70