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	$91.29	7.272%	$97.9286	$97.93	$97.95	$97.90
Purchase #2	$222.93	11.307%	$248.1367	$248.14	$248.15	$248.10
Purchase #3	$175.90	7.320%	$188.7759	$188.78	$188.80	$188.80
Purchase #4	$139.47	9.607%	$152.8689	$152.87	$152.85	$152.90
Purchase #5	$133.53	4.106%	$139.0127	$139.01	$139.00	$139.00
Purchase #6	$52.56	5.106%	$55.2437	$55.24	$55.25	$55.20
Purchase #7	$32.44	3.414%	$33.5475	$33.55	$33.55	$33.50
7 purchase totals =	$848.12		$915.5140	$915.52	$915.55	$915.40