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	$152.65	8.506%	$165.6344	$165.63	$165.65	$165.60
Purchase #2	$52.78	5.342%	$55.5995	$55.60	$55.60	$55.60
Purchase #3	$16.70	12.478%	$18.7838	$18.78	$18.80	$18.80
Purchase #4	$192.99	11.801%	$215.7647	$215.76	$215.75	$215.80
Purchase #5	$162.44	3.481%	$168.0945	$168.09	$168.10	$168.10
Purchase #6	$180.55	3.628%	$187.1004	$187.10	$187.10	$187.10
Purchase #7	$237.70	6.821%	$253.9135	$253.91	$253.90	$253.90
7 purchase totals =	$995.81		$1,064.8908	$1,064.87	$1,064.90	$1,064.90