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	$155.88	4.413%	$162.759	$162.76	$162.75	$162.80
Purchase #2	$38.49	6.273%	$40.9045	$40.90	$40.90	$40.90
Purchase #3	$100.97	4.258%	$105.2693	$105.27	$105.25	$105.30
Purchase #4	$126.33	8.201%	$136.6903	$136.69	$136.70	$136.70
Purchase #5	$213.58	12.754%	$240.82	$240.82	$240.80	$240.80
Purchase #6	$58.71	10.748%	$65.0202	$65.02	$65.00	$65.00
Purchase #7	$223.25	3.531%	$231.133	$231.13	$231.15	$231.10
7 purchase totals =	$917.21		$982.5963	$982.59	$982.55	$982.60