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	$214.25	3.799%	$222.3894	$222.39	$222.40	$222.40
Purchase #2	$85.97	5.711%	$90.8797	$90.88	$90.90	$90.90
Purchase #3	$168.53	11.270%	$187.5233	$187.52	$187.50	$187.50
Purchase #4	$166.92	4.650%	$174.6818	$174.68	$174.70	$174.70
Purchase #5	$143.82	5.234%	$151.3475	$151.35	$151.35	$151.30
Purchase #6	$57.86	5.665%	$61.1378	$61.14	$61.15	$61.10
Purchase #7	$52.50	4.530%	$54.8783	$54.88	$54.90	$54.90
7 purchase totals =	$889.85		$942.8378	$942.84	$942.90	$942.80