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	$209.38	6.421%	$222.8243	$222.82	$222.80	$222.80
Purchase #2	$235.70	10.435%	$260.2953	$260.30	$260.30	$260.30
Purchase #3	$149.81	4.542%	$156.6144	$156.61	$156.60	$156.60
Purchase #4	$102.87	3.540%	$106.5116	$106.51	$106.50	$106.50
Purchase #5	$86.92	11.447%	$96.8697	$96.87	$96.85	$96.90
Purchase #6	$50.63	9.442%	$55.4105	$55.41	$55.40	$55.40
Purchase #7	$97.25	12.834%	$109.7311	$109.73	$109.75	$109.70
7 purchase totals =	$932.56		$1,008.2569	$1,008.25	$1,008.20	$1,008.20