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	$89.50	9.670%	$98.1547	$98.15	$98.15	$98.20
Purchase #2	$95.28	5.722%	$100.7319	$100.73	$100.75	$100.70
Purchase #3	$176.54	6.870%	$188.6683	$188.67	$188.65	$188.70
Purchase #4	$129.57	9.863%	$142.3495	$142.35	$142.35	$142.30
Purchase #5	$34.50	9.873%	$37.9062	$37.91	$37.90	$37.90
Purchase #6	$234.85	5.162%	$246.973	$246.97	$246.95	$247.00
Purchase #7	$142.67	5.465%	$150.4669	$150.47	$150.45	$150.50
7 purchase totals =	$902.91		$965.2505	$965.25	$965.20	$965.30