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	$158.86	7.569%	$170.8841	$170.88	$170.90	$170.90
Purchase #2	$40.99	4.148%	$42.6903	$42.69	$42.70	$42.70
Purchase #3	$83.90	6.437%	$89.3006	$89.30	$89.30	$89.30
Purchase #4	$41.83	7.577%	$44.9995	$45.00	$45.00	$45.00
Purchase #5	$161.97	11.244%	$180.1819	$180.18	$180.20	$180.20
Purchase #6	$74.53	12.155%	$83.5891	$83.59	$83.60	$83.60
Purchase #7	$153.31	3.171%	$158.1715	$158.17	$158.15	$158.20
7 purchase totals =	$715.39		$769.8170	$769.81	$769.85	$769.90