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	$113.35	9.287%	$123.8768	$123.88	$123.90	$123.90
Purchase #2	$133.94	12.179%	$150.2526	$150.25	$150.25	$150.30
Purchase #3	$9.48	10.199%	$10.4469	$10.45	$10.45	$10.40
Purchase #4	$73.52	11.485%	$81.9638	$81.96	$81.95	$82.00
Purchase #5	$27.69	4.253%	$28.8677	$28.87	$28.85	$28.90
Purchase #6	$132.71	11.265%	$147.6598	$147.66	$147.65	$147.70
Purchase #7	$144.91	5.442%	$152.796	$152.80	$152.80	$152.80
7 purchase totals =	$635.60		$695.8636	$695.87	$695.85	$696.00