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	$153.35	10.520%	$169.4824	$169.48	$169.50	$169.50
Purchase #2	$65.51	11.376%	$72.9624	$72.96	$72.95	$73.00
Purchase #3	$89.57	5.695%	$94.671	$94.67	$94.65	$94.70
Purchase #4	$98.77	4.783%	$103.4942	$103.49	$103.50	$103.50
Purchase #5	$80.51	7.755%	$86.7536	$86.75	$86.75	$86.80
Purchase #6	$65.56	8.610%	$71.2047	$71.20	$71.20	$71.20
Purchase #7	$82.45	6.494%	$87.8043	$87.80	$87.80	$87.80
7 purchase totals =	$635.72		$686.3726	$686.35	$686.35	$686.50