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	$146.51	8.359%	$158.7568	$158.76	$158.75	$158.80
Purchase #2	$225.83	13.216%	$255.6757	$255.68	$255.70	$255.70
Purchase #3	$152.45	10.589%	$168.5929	$168.59	$168.60	$168.60
Purchase #4	$105.66	6.657%	$112.6938	$112.69	$112.70	$112.70
Purchase #5	$183.31	5.770%	$193.887	$193.89	$193.90	$193.90
Purchase #6	$71.92	11.770%	$80.385	$80.39	$80.40	$80.40
Purchase #7	$115.47	4.684%	$120.8786	$120.88	$120.90	$120.90
7 purchase totals =	$1,001.15		$1,090.8698	$1,090.88	$1,090.95	$1,091.00