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	$123.72	10.860%	$137.156	$137.16	$137.15	$137.20
Purchase #2	$196.27	4.419%	$204.9432	$204.94	$204.95	$204.90
Purchase #3	$136.96	9.823%	$150.4136	$150.41	$150.40	$150.40
Purchase #4	$20.95	3.297%	$21.6407	$21.64	$21.65	$21.60
Purchase #5	$247.98	9.258%	$270.938	$270.94	$270.95	$270.90
Purchase #6	$172.75	8.487%	$187.4113	$187.41	$187.40	$187.40
Purchase #7	$193.93	3.609%	$200.9289	$200.93	$200.95	$200.90
7 purchase totals =	$1,092.56		$1,173.4317	$1,173.43	$1,173.45	$1,173.30