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	$174.94	10.237%	$192.8486	$192.85	$192.85	$192.80
Purchase #2	$85.78	7.751%	$92.4288	$92.43	$92.45	$92.40
Purchase #3	$57.34	13.720%	$65.207	$65.21	$65.20	$65.20
Purchase #4	$144.54	11.164%	$160.6764	$160.68	$160.70	$160.70
Purchase #5	$69.65	13.192%	$78.8382	$78.84	$78.85	$78.80
Purchase #6	$56.89	13.725%	$64.6982	$64.70	$64.70	$64.70
Purchase #7	$172.72	9.859%	$189.7485	$189.75	$189.75	$189.70
7 purchase totals =	$761.86		$844.4457	$844.46	$844.50	$844.30