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	$58.48	11.615%	$65.2725	$65.27	$65.25	$65.30
Purchase #2	$146.80	6.804%	$156.7883	$156.79	$156.80	$156.80
Purchase #3	$221.54	5.675%	$234.1124	$234.11	$234.10	$234.10
Purchase #4	$174.96	8.466%	$189.7721	$189.77	$189.75	$189.80
Purchase #5	$77.31	10.475%	$85.4082	$85.41	$85.40	$85.40
Purchase #6	$40.74	3.200%	$42.0437	$42.04	$42.05	$42.00
Purchase #7	$241.63	12.724%	$272.375	$272.38	$272.40	$272.40
7 purchase totals =	$961.46		$1,045.7722	$1,045.77	$1,045.75	$1,045.80