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	$35.38	6.471%	$37.6694	$37.67	$37.65	$37.70
Purchase #2	$87.98	11.245%	$97.8734	$97.87	$97.85	$97.90
Purchase #3	$52.27	5.236%	$55.0069	$55.01	$55.00	$55.00
Purchase #4	$175.25	5.503%	$184.894	$184.89	$184.90	$184.90
Purchase #5	$86.52	8.690%	$94.0386	$94.04	$94.05	$94.00
Purchase #6	$115.33	11.140%	$128.1778	$128.18	$128.20	$128.20
Purchase #7	$84.49	4.507%	$88.298	$88.30	$88.30	$88.30
7 purchase totals =	$637.22		$685.9581	$685.96	$685.95	$686.00