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	$132.51	11.686%	$147.9951	$148.00	$148.00	$148.00
Purchase #2	$145.95	4.552%	$152.5936	$152.59	$152.60	$152.60
Purchase #3	$131.94	4.553%	$137.9472	$137.95	$137.95	$137.90
Purchase #4	$71.28	5.624%	$75.2888	$75.29	$75.30	$75.30
Purchase #5	$94.76	12.150%	$106.2733	$106.27	$106.25	$106.30
Purchase #6	$90.90	10.632%	$100.5645	$100.56	$100.55	$100.60
Purchase #7	$83.30	4.374%	$86.9435	$86.94	$86.95	$86.90
7 purchase totals =	$750.64		$807.6060	$807.60	$807.60	$807.60