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	$105.44	6.196%	$111.9731	$111.97	$111.95	$112.00
Purchase #2	$75.58	13.565%	$85.8324	$85.83	$85.85	$85.80
Purchase #3	$206.79	5.468%	$218.0973	$218.10	$218.10	$218.10
Purchase #4	$193.88	12.726%	$218.5532	$218.55	$218.55	$218.60
Purchase #5	$73.60	4.396%	$76.8355	$76.84	$76.85	$76.80
Purchase #6	$223.65	5.280%	$235.4587	$235.46	$235.45	$235.50
Purchase #7	$125.29	6.818%	$133.8323	$133.83	$133.85	$133.80
7 purchase totals =	$1,004.23		$1,080.5825	$1,080.58	$1,080.60	$1,080.60