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	$162.25	10.666%	$179.5556	$179.56	$179.55	$179.60
Purchase #2	$75.50	9.613%	$82.7578	$82.76	$82.75	$82.80
Purchase #3	$6.54	5.668%	$6.9107	$6.91	$6.90	$6.90
Purchase #4	$16.69	12.514%	$18.7786	$18.78	$18.80	$18.80
Purchase #5	$10.88	5.311%	$11.4578	$11.46	$11.45	$11.50
Purchase #6	$123.98	6.819%	$132.4342	$132.43	$132.45	$132.40
Purchase #7	$170.56	7.206%	$182.8506	$182.85	$182.85	$182.90
7 purchase totals =	$566.40		$614.7453	$614.75	$614.75	$614.90