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	$134.70	9.238%	$147.1436	$147.14	$147.15	$147.10
Purchase #2	$118.55	6.639%	$126.4205	$126.42	$126.40	$126.40
Purchase #3	$82.30	4.801%	$86.2512	$86.25	$86.25	$86.30
Purchase #4	$33.67	11.698%	$37.6087	$37.61	$37.60	$37.60
Purchase #5	$129.34	10.568%	$143.0087	$143.01	$143.00	$143.00
Purchase #6	$151.88	9.367%	$166.1066	$166.11	$166.10	$166.10
Purchase #7	$18.83	8.462%	$20.4234	$20.42	$20.40	$20.40
7 purchase totals =	$669.27		$726.9627	$726.96	$726.90	$726.90