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	$213.90	4.496%	$223.5169	$223.52	$223.50	$223.50
Purchase #2	$235.37	10.287%	$259.5825	$259.58	$259.60	$259.60
Purchase #3	$28.42	9.552%	$31.1347	$31.13	$31.15	$31.10
Purchase #4	$92.60	11.412%	$103.1675	$103.17	$103.15	$103.20
Purchase #5	$195.43	9.156%	$213.3236	$213.32	$213.30	$213.30
Purchase #6	$16.25	6.262%	$17.2676	$17.27	$17.25	$17.30
Purchase #7	$169.58	12.643%	$191.02	$191.02	$191.00	$191.00
7 purchase totals =	$951.55		$1,039.0128	$1,039.01	$1,038.95	$1,039.00