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	$97.27	4.265%	$101.4186	$101.42	$101.40	$101.40
Purchase #2	$65.75	10.514%	$72.663	$72.66	$72.65	$72.70
Purchase #3	$46.86	9.421%	$51.2747	$51.27	$51.25	$51.30
Purchase #4	$132.38	10.404%	$146.1528	$146.15	$146.15	$146.20
Purchase #5	$218.91	4.372%	$228.4807	$228.48	$228.50	$228.50
Purchase #6	$162.64	5.727%	$171.9544	$171.95	$171.95	$172.00
Purchase #7	$36.70	5.172%	$38.5981	$38.60	$38.60	$38.60
7 purchase totals =	$760.51		$810.5423	$810.53	$810.50	$810.70