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	$169.78	9.519%	$185.9414	$185.94	$185.95	$185.90
Purchase #2	$20.93	10.398%	$23.1063	$23.11	$23.10	$23.10
Purchase #3	$160.74	6.187%	$170.685	$170.69	$170.70	$170.70
Purchase #4	$27.71	7.836%	$29.8814	$29.88	$29.90	$29.90
Purchase #5	$95.69	3.804%	$99.33	$99.33	$99.35	$99.30
Purchase #6	$182.91	9.845%	$200.9175	$200.92	$200.90	$200.90
Purchase #7	$10.39	11.133%	$11.5467	$11.55	$11.55	$11.50
7 purchase totals =	$668.15		$721.4083	$721.42	$721.45	$721.30