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	$95.37	4.325%	$99.4948	$99.49	$99.50	$99.50
Purchase #2	$117.75	10.269%	$129.8417	$129.84	$129.85	$129.80
Purchase #3	$16.34	10.814%	$18.107	$18.11	$18.10	$18.10
Purchase #4	$80.26	11.515%	$89.5019	$89.50	$89.50	$89.50
Purchase #5	$128.81	8.718%	$140.0397	$140.04	$140.05	$140.00
Purchase #6	$111.37	5.221%	$117.1846	$117.18	$117.20	$117.20
Purchase #7	$76.32	7.494%	$82.0394	$82.04	$82.05	$82.00
7 purchase totals =	$626.22		$676.2091	$676.20	$676.25	$676.10