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	$175.91	8.722%	$191.2529	$191.25	$191.25	$191.30
Purchase #2	$32.89	10.649%	$36.3925	$36.39	$36.40	$36.40
Purchase #3	$111.89	13.584%	$127.0891	$127.09	$127.10	$127.10
Purchase #4	$212.66	5.587%	$224.5413	$224.54	$224.55	$224.50
Purchase #5	$43.85	5.834%	$46.4082	$46.41	$46.40	$46.40
Purchase #6	$80.47	6.588%	$85.7714	$85.77	$85.75	$85.80
Purchase #7	$163.70	3.561%	$169.5294	$169.53	$169.55	$169.50
7 purchase totals =	$821.37		$880.9848	$880.98	$881.00	$881.00