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	$56.60	6.795%	$60.446	$60.45	$60.45	$60.40
Purchase #2	$175.60	3.715%	$182.1235	$182.12	$182.10	$182.10
Purchase #3	$137.89	5.409%	$145.3485	$145.35	$145.35	$145.30
Purchase #4	$87.46	4.328%	$91.2453	$91.25	$91.25	$91.20
Purchase #5	$220.52	7.652%	$237.3942	$237.39	$237.40	$237.40
Purchase #6	$184.90	5.200%	$194.5148	$194.51	$194.50	$194.50
Purchase #7	$146.49	4.318%	$152.8154	$152.82	$152.80	$152.80
7 purchase totals =	$1,009.46		$1,063.8877	$1,063.89	$1,063.85	$1,063.70