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	$204.52	4.262%	$213.2366	$213.24	$213.25	$213.20
Purchase #2	$130.96	13.353%	$148.4471	$148.45	$148.45	$148.40
Purchase #3	$80.33	6.333%	$85.4173	$85.42	$85.40	$85.40
Purchase #4	$215.75	5.490%	$227.5947	$227.59	$227.60	$227.60
Purchase #5	$192.38	8.768%	$209.2479	$209.25	$209.25	$209.20
Purchase #6	$29.27	13.679%	$33.2738	$33.27	$33.25	$33.30
Purchase #7	$173.84	3.706%	$180.2825	$180.28	$180.30	$180.30
7 purchase totals =	$1,027.05		$1,097.4999	$1,097.50	$1,097.50	$1,097.40