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	$225.28	7.597%	$242.3945	$242.39	$242.40	$242.40
Purchase #2	$210.40	8.798%	$228.911	$228.91	$228.90	$228.90
Purchase #3	$7.37	9.810%	$8.093	$8.09	$8.10	$8.10
Purchase #4	$185.89	4.822%	$194.8536	$194.85	$194.85	$194.90
Purchase #5	$212.49	3.349%	$219.6063	$219.61	$219.60	$219.60
Purchase #6	$140.83	8.564%	$152.8907	$152.89	$152.90	$152.90
Purchase #7	$201.88	3.274%	$208.4896	$208.49	$208.50	$208.50
7 purchase totals =	$1,184.14		$1,255.2387	$1,255.23	$1,255.25	$1,255.30