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	$185.91	6.435%	$197.8733	$197.87	$197.85	$197.90
Purchase #2	$45.89	4.379%	$47.8995	$47.90	$47.90	$47.90
Purchase #3	$154.91	10.466%	$171.1229	$171.12	$171.10	$171.10
Purchase #4	$86.95	3.651%	$90.1245	$90.12	$90.10	$90.10
Purchase #5	$90.89	4.187%	$94.6956	$94.70	$94.70	$94.70
Purchase #6	$111.61	12.761%	$125.8526	$125.85	$125.85	$125.90
Purchase #7	$37.42	6.436%	$39.8284	$39.83	$39.85	$39.80
7 purchase totals =	$713.58		$767.3968	$767.39	$767.35	$767.40