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	$151.32	4.583%	$158.255	$158.26	$158.25	$158.30
Purchase #2	$203.42	7.607%	$218.8942	$218.89	$218.90	$218.90
Purchase #3	$18.87	7.844%	$20.3502	$20.35	$20.35	$20.40
Purchase #4	$110.45	10.523%	$122.0727	$122.07	$122.05	$122.10
Purchase #5	$151.87	6.177%	$161.251	$161.25	$161.25	$161.30
Purchase #6	$190.30	3.153%	$196.3002	$196.30	$196.30	$196.30
Purchase #7	$164.81	10.507%	$182.1266	$182.13	$182.15	$182.10
7 purchase totals =	$991.04		$1,059.2499	$1,059.25	$1,059.25	$1,059.40