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	$206.69	4.293%	$215.5632	$215.56	$215.55	$215.60
Purchase #2	$19.33	9.463%	$21.1592	$21.16	$21.15	$21.20
Purchase #3	$25.71	4.785%	$26.9402	$26.94	$26.95	$26.90
Purchase #4	$127.78	13.376%	$144.8719	$144.87	$144.85	$144.90
Purchase #5	$176.56	11.538%	$196.9315	$196.93	$196.95	$196.90
Purchase #6	$140.55	6.689%	$149.9514	$149.95	$149.95	$150.00
Purchase #7	$192.28	10.824%	$213.0924	$213.09	$213.10	$213.10
7 purchase totals =	$888.90		$968.5098	$968.50	$968.50	$968.60