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	$98.38	5.353%	$103.6463	$103.65	$103.65	$103.60
Purchase #2	$7.95	6.412%	$8.4598	$8.46	$8.45	$8.50
Purchase #3	$65.53	9.520%	$71.7685	$71.77	$71.75	$71.80
Purchase #4	$223.27	8.529%	$242.3127	$242.31	$242.30	$242.30
Purchase #5	$143.52	13.205%	$162.4718	$162.47	$162.45	$162.50
Purchase #6	$29.87	13.655%	$33.9487	$33.95	$33.95	$33.90
Purchase #7	$231.31	12.146%	$259.4049	$259.40	$259.40	$259.40
7 purchase totals =	$799.83		$882.0127	$882.01	$881.95	$882.00