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	$82.79	7.598%	$89.0804	$89.08	$89.10	$89.10
Purchase #2	$217.37	13.577%	$246.8823	$246.88	$246.90	$246.90
Purchase #3	$168.91	7.515%	$181.6036	$181.60	$181.60	$181.60
Purchase #4	$163.50	3.152%	$168.6535	$168.65	$168.65	$168.70
Purchase #5	$220.77	9.337%	$241.3833	$241.38	$241.40	$241.40
Purchase #6	$28.55	7.208%	$30.6079	$30.61	$30.60	$30.60
Purchase #7	$72.39	13.393%	$82.0852	$82.09	$82.10	$82.10
7 purchase totals =	$954.28		$1,040.2962	$1,040.29	$1,040.35	$1,040.40