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	$140.95	4.161%	$146.8149	$146.81	$146.80	$146.80
Purchase #2	$94.76	7.314%	$101.6907	$101.69	$101.70	$101.70
Purchase #3	$229.27	7.520%	$246.5111	$246.51	$246.50	$246.50
Purchase #4	$19.38	9.542%	$21.2292	$21.23	$21.25	$21.20
Purchase #5	$168.42	3.403%	$174.1513	$174.15	$174.15	$174.20
Purchase #6	$171.46	6.698%	$182.9444	$182.94	$182.95	$182.90
Purchase #7	$167.29	12.613%	$188.3903	$188.39	$188.40	$188.40
7 purchase totals =	$991.53		$1,061.7319	$1,061.72	$1,061.75	$1,061.70