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	$175.90	5.733%	$185.9843	$185.98	$186.00	$186.00
Purchase #2	$151.25	7.595%	$162.7374	$162.74	$162.75	$162.70
Purchase #3	$248.74	4.836%	$260.7691	$260.77	$260.75	$260.80
Purchase #4	$165.98	11.389%	$184.8835	$184.88	$184.90	$184.90
Purchase #5	$76.33	9.389%	$83.4966	$83.50	$83.50	$83.50
Purchase #6	$174.47	12.831%	$196.8562	$196.86	$196.85	$196.90
Purchase #7	$154.66	3.358%	$159.8535	$159.85	$159.85	$159.90
7 purchase totals =	$1,147.33		$1,234.5806	$1,234.58	$1,234.60	$1,234.70