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	$80.97	13.590%	$91.9738	$91.97	$91.95	$92.00
Purchase #2	$52.46	8.334%	$56.832	$56.83	$56.85	$56.80
Purchase #3	$55.61	7.140%	$59.5806	$59.58	$59.60	$59.60
Purchase #4	$83.60	6.390%	$88.942	$88.94	$88.95	$88.90
Purchase #5	$109.37	9.679%	$119.9559	$119.96	$119.95	$120.00
Purchase #6	$87.62	4.550%	$91.6067	$91.61	$91.60	$91.60
Purchase #7	$170.69	5.550%	$180.1633	$180.16	$180.15	$180.20
7 purchase totals =	$640.32		$689.0543	$689.05	$689.05	$689.10