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	$68.73	8.158%	$74.337	$74.34	$74.35	$74.30
Purchase #2	$6.28	11.740%	$7.0173	$7.02	$7.00	$7.00
Purchase #3	$161.93	12.320%	$181.8798	$181.88	$181.90	$181.90
Purchase #4	$134.78	7.467%	$144.844	$144.84	$144.85	$144.80
Purchase #5	$216.89	6.538%	$231.0703	$231.07	$231.05	$231.10
Purchase #6	$151.43	7.309%	$162.498	$162.50	$162.50	$162.50
Purchase #7	$52.34	4.334%	$54.6084	$54.61	$54.60	$54.60
7 purchase totals =	$792.38		$856.2548	$856.26	$856.25	$856.20