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	$228.74	11.780%	$255.6856	$255.69	$255.70	$255.70
Purchase #2	$85.35	6.616%	$90.9968	$91.00	$91.00	$91.00
Purchase #3	$83.65	9.386%	$91.5014	$91.50	$91.50	$91.50
Purchase #4	$48.40	9.545%	$53.0198	$53.02	$53.00	$53.00
Purchase #5	$41.93	6.576%	$44.6873	$44.69	$44.70	$44.70
Purchase #6	$57.70	3.241%	$59.5701	$59.57	$59.55	$59.60
Purchase #7	$17.69	10.395%	$19.5289	$19.53	$19.55	$19.50
7 purchase totals =	$563.46		$614.9899	$615.00	$615.00	$615.00