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	$36.98	3.580%	$38.3039	$38.30	$38.30	$38.30
Purchase #2	$82.72	5.299%	$87.1033	$87.10	$87.10	$87.10
Purchase #3	$88.50	12.205%	$99.3014	$99.30	$99.30	$99.30
Purchase #4	$69.93	13.601%	$79.4412	$79.44	$79.45	$79.40
Purchase #5	$120.35	4.234%	$125.4456	$125.45	$125.45	$125.40
Purchase #6	$137.42	13.629%	$156.149	$156.15	$156.15	$156.10
Purchase #7	$81.75	10.506%	$90.3387	$90.34	$90.35	$90.30
7 purchase totals =	$617.65		$676.0831	$676.08	$676.10	$675.90