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	$31.85	8.571%	$34.5799	$34.58	$34.60	$34.60
Purchase #2	$155.40	7.722%	$167.4	$167.40	$167.40	$167.40
Purchase #3	$86.92	3.260%	$89.7536	$89.75	$89.75	$89.80
Purchase #4	$222.67	10.849%	$246.8275	$246.83	$246.85	$246.80
Purchase #5	$244.32	8.180%	$264.3054	$264.31	$264.30	$264.30
Purchase #6	$175.99	5.337%	$185.3826	$185.38	$185.40	$185.40
Purchase #7	$235.60	8.351%	$255.275	$255.28	$255.30	$255.30
7 purchase totals =	$1,152.75		$1,243.5240	$1,243.53	$1,243.60	$1,243.60