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	$107.26	5.443%	$113.0982	$113.10	$113.10	$113.10
Purchase #2	$135.80	10.826%	$150.5017	$150.50	$150.50	$150.50
Purchase #3	$213.96	9.748%	$234.8168	$234.82	$234.80	$234.80
Purchase #4	$202.81	10.171%	$223.4378	$223.44	$223.45	$223.40
Purchase #5	$92.55	10.579%	$102.3409	$102.34	$102.35	$102.30
Purchase #6	$72.58	13.195%	$82.1569	$82.16	$82.15	$82.20
Purchase #7	$78.96	9.666%	$86.5923	$86.59	$86.60	$86.60
7 purchase totals =	$903.92		$992.9446	$992.95	$992.95	$992.90