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	$54.27	12.439%	$61.0206	$61.02	$61.00	$61.00
Purchase #2	$229.29	11.192%	$254.9521	$254.95	$254.95	$255.00
Purchase #3	$121.34	4.277%	$126.5297	$126.53	$126.55	$126.50
Purchase #4	$204.39	6.827%	$218.3437	$218.34	$218.35	$218.30
Purchase #5	$59.87	5.136%	$62.9449	$62.94	$62.95	$62.90
Purchase #6	$83.88	7.147%	$89.8749	$89.87	$89.85	$89.90
Purchase #7	$18.34	3.823%	$19.0411	$19.04	$19.05	$19.00
7 purchase totals =	$771.38		$832.7070	$832.69	$832.70	$832.60