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	$175.90	5.687%	$185.9034	$185.90	$185.90	$185.90
Purchase #2	$90.49	10.858%	$100.3154	$100.32	$100.30	$100.30
Purchase #3	$51.71	10.393%	$57.0842	$57.08	$57.10	$57.10
Purchase #4	$29.79	12.579%	$33.5373	$33.54	$33.55	$33.50
Purchase #5	$172.86	3.531%	$178.9637	$178.96	$178.95	$179.00
Purchase #6	$189.94	5.751%	$200.8634	$200.86	$200.85	$200.90
Purchase #7	$109.92	11.249%	$122.2849	$122.28	$122.30	$122.30
7 purchase totals =	$820.61		$878.9523	$878.94	$878.95	$879.00