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	$68.83	4.557%	$71.9666	$71.97	$71.95	$72.00
Purchase #2	$187.89	4.573%	$196.4822	$196.48	$196.50	$196.50
Purchase #3	$160.46	7.688%	$172.7962	$172.80	$172.80	$172.80
Purchase #4	$104.43	11.442%	$116.3789	$116.38	$116.40	$116.40
Purchase #5	$164.75	13.816%	$187.5119	$187.51	$187.50	$187.50
Purchase #6	$81.68	10.574%	$90.3168	$90.32	$90.30	$90.30
Purchase #7	$120.86	6.694%	$128.9504	$128.95	$128.95	$129.00
7 purchase totals =	$888.90		$964.4030	$964.41	$964.40	$964.50