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	$181.28	8.196%	$196.1377	$196.14	$196.15	$196.10
Purchase #2	$245.52	6.768%	$262.1368	$262.14	$262.15	$262.10
Purchase #3	$138.47	8.769%	$150.6124	$150.61	$150.60	$150.60
Purchase #4	$18.71	10.112%	$20.602	$20.60	$20.60	$20.60
Purchase #5	$119.69	7.480%	$128.6428	$128.64	$128.65	$128.60
Purchase #6	$158.85	6.289%	$168.8401	$168.84	$168.85	$168.80
Purchase #7	$143.26	12.417%	$161.0486	$161.05	$161.05	$161.00
7 purchase totals =	$1,005.78		$1,088.0204	$1,088.02	$1,088.05	$1,087.80