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	$223.96	13.638%	$254.5037	$254.50	$254.50	$254.50
Purchase #2	$108.58	11.296%	$120.8452	$120.85	$120.85	$120.80
Purchase #3	$52.93	9.318%	$57.862	$57.86	$57.85	$57.90
Purchase #4	$247.67	13.805%	$281.8608	$281.86	$281.85	$281.90
Purchase #5	$102.63	9.150%	$112.0206	$112.02	$112.00	$112.00
Purchase #6	$68.49	5.739%	$72.4206	$72.42	$72.40	$72.40
Purchase #7	$95.36	10.303%	$105.1849	$105.18	$105.20	$105.20
7 purchase totals =	$899.62		$1,004.6978	$1,004.69	$1,004.65	$1,004.70