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	$176.77	11.329%	$196.7963	$196.80	$196.80	$196.80
Purchase #2	$65.87	10.411%	$72.7277	$72.73	$72.75	$72.70
Purchase #3	$49.82	8.674%	$54.1414	$54.14	$54.15	$54.10
Purchase #4	$96.69	12.141%	$108.4291	$108.43	$108.45	$108.40
Purchase #5	$31.80	9.494%	$34.8191	$34.82	$34.80	$34.80
Purchase #6	$137.88	9.279%	$150.6739	$150.67	$150.65	$150.70
Purchase #7	$191.53	7.480%	$205.8564	$205.86	$205.85	$205.90
7 purchase totals =	$750.36		$823.4439	$823.45	$823.45	$823.40