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	$109.51	8.384%	$118.6913	$118.69	$118.70	$118.70
Purchase #2	$158.54	6.357%	$168.6184	$168.62	$168.60	$168.60
Purchase #3	$57.75	3.529%	$59.788	$59.79	$59.80	$59.80
Purchase #4	$205.81	8.238%	$222.7646	$222.76	$222.75	$222.80
Purchase #5	$222.64	8.503%	$241.5711	$241.57	$241.55	$241.60
Purchase #6	$65.76	8.676%	$71.4653	$71.47	$71.45	$71.50
Purchase #7	$180.53	3.227%	$186.3557	$186.36	$186.35	$186.40
7 purchase totals =	$1,000.54		$1,069.2544	$1,069.26	$1,069.20	$1,069.40