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	$159.40	5.630%	$168.3742	$168.37	$168.35	$168.40
Purchase #2	$215.61	8.485%	$233.9045	$233.90	$233.90	$233.90
Purchase #3	$61.78	10.639%	$68.3528	$68.35	$68.35	$68.40
Purchase #4	$82.75	8.502%	$89.7854	$89.79	$89.80	$89.80
Purchase #5	$229.46	5.230%	$241.4608	$241.46	$241.45	$241.50
Purchase #6	$164.91	12.368%	$185.3061	$185.31	$185.30	$185.30
Purchase #7	$83.36	4.587%	$87.1837	$87.18	$87.20	$87.20
7 purchase totals =	$997.27		$1,074.3675	$1,074.36	$1,074.35	$1,074.50