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	$89.29	3.548%	$92.458	$92.46	$92.45	$92.50
Purchase #2	$243.49	4.785%	$255.141	$255.14	$255.15	$255.10
Purchase #3	$249.61	10.158%	$274.9654	$274.97	$274.95	$275.00
Purchase #4	$204.94	5.748%	$216.72	$216.72	$216.70	$216.70
Purchase #5	$70.30	11.587%	$78.4457	$78.45	$78.45	$78.40
Purchase #6	$41.48	3.740%	$43.0314	$43.03	$43.05	$43.00
Purchase #7	$177.46	10.508%	$196.1075	$196.11	$196.10	$196.10
7 purchase totals =	$1,076.57		$1,156.8690	$1,156.88	$1,156.85	$1,156.80