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	$242.42	12.182%	$271.9516	$271.95	$271.95	$272.00
Purchase #2	$191.43	10.698%	$211.9092	$211.91	$211.90	$211.90
Purchase #3	$157.73	13.527%	$179.0661	$179.07	$179.05	$179.10
Purchase #4	$247.30	4.330%	$258.0081	$258.01	$258.00	$258.00
Purchase #5	$56.33	3.759%	$58.4474	$58.45	$58.45	$58.40
Purchase #6	$58.93	6.333%	$62.662	$62.66	$62.65	$62.70
Purchase #7	$118.72	11.113%	$131.9134	$131.91	$131.90	$131.90
7 purchase totals =	$1,072.86		$1,173.9578	$1,173.96	$1,173.90	$1,174.00