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	$151.47	7.212%	$162.394	$162.39	$162.40	$162.40
Purchase #2	$34.38	9.790%	$37.7458	$37.75	$37.75	$37.70
Purchase #3	$167.62	13.538%	$190.3124	$190.31	$190.30	$190.30
Purchase #4	$154.42	3.212%	$159.38	$159.38	$159.40	$159.40
Purchase #5	$55.66	9.171%	$60.7646	$60.76	$60.75	$60.80
Purchase #6	$150.96	11.835%	$168.8261	$168.83	$168.85	$168.80
Purchase #7	$110.31	7.324%	$118.3891	$118.39	$118.40	$118.40
7 purchase totals =	$824.82		$897.8120	$897.81	$897.85	$897.80