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	$165.93	3.811%	$172.2536	$172.25	$172.25	$172.30
Purchase #2	$89.79	9.704%	$98.5032	$98.50	$98.50	$98.50
Purchase #3	$5.36	4.557%	$5.6043	$5.60	$5.60	$5.60
Purchase #4	$40.99	13.523%	$46.5331	$46.53	$46.55	$46.50
Purchase #5	$62.94	13.223%	$71.2626	$71.26	$71.25	$71.30
Purchase #6	$153.93	5.666%	$162.6517	$162.65	$162.65	$162.70
Purchase #7	$49.74	7.337%	$53.3894	$53.39	$53.40	$53.40
7 purchase totals =	$568.68		$610.1979	$610.18	$610.20	$610.30