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	$60.95	11.164%	$67.7545	$67.75	$67.75	$67.80
Purchase #2	$180.60	4.629%	$188.96	$188.96	$188.95	$189.00
Purchase #3	$101.85	12.406%	$114.4855	$114.49	$114.50	$114.50
Purchase #4	$190.29	9.818%	$208.9727	$208.97	$208.95	$209.00
Purchase #5	$41.82	8.831%	$45.5131	$45.51	$45.50	$45.50
Purchase #6	$37.35	3.862%	$38.7925	$38.79	$38.80	$38.80
Purchase #7	$94.31	13.373%	$106.9221	$106.92	$106.90	$106.90
7 purchase totals =	$707.17		$771.4004	$771.39	$771.35	$771.50