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	$113.86	3.529%	$117.8781	$117.88	$117.90	$117.90
Purchase #2	$201.28	10.703%	$222.823	$222.82	$222.80	$222.80
Purchase #3	$57.58	7.419%	$61.8519	$61.85	$61.85	$61.90
Purchase #4	$151.53	4.614%	$158.5216	$158.52	$158.50	$158.50
Purchase #5	$242.57	6.323%	$257.9077	$257.91	$257.90	$257.90
Purchase #6	$146.46	11.151%	$162.7918	$162.79	$162.80	$162.80
Purchase #7	$226.42	7.719%	$243.8974	$243.90	$243.90	$243.90
7 purchase totals =	$1,139.70		$1,225.6715	$1,225.67	$1,225.65	$1,225.70