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	$77.74	5.530%	$82.039	$82.04	$82.05	$82.00
Purchase #2	$215.53	12.789%	$243.0941	$243.09	$243.10	$243.10
Purchase #3	$133.88	6.464%	$142.534	$142.53	$142.55	$142.50
Purchase #4	$180.76	5.472%	$190.6512	$190.65	$190.65	$190.70
Purchase #5	$239.28	3.635%	$247.9778	$247.98	$248.00	$248.00
Purchase #6	$153.82	6.811%	$164.2967	$164.30	$164.30	$164.30
Purchase #7	$209.62	9.622%	$229.7896	$229.79	$229.80	$229.80
7 purchase totals =	$1,210.63		$1,300.3824	$1,300.38	$1,300.45	$1,300.40