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	$104.78	4.520%	$109.5161	$109.52	$109.50	$109.50
Purchase #2	$134.32	4.639%	$140.5511	$140.55	$140.55	$140.60
Purchase #3	$217.62	13.349%	$246.6701	$246.67	$246.65	$246.70
Purchase #4	$55.27	12.206%	$62.0163	$62.02	$62.00	$62.00
Purchase #5	$100.83	4.790%	$105.6598	$105.66	$105.65	$105.70
Purchase #6	$226.43	7.458%	$243.3171	$243.32	$243.30	$243.30
Purchase #7	$144.47	5.509%	$152.4289	$152.43	$152.45	$152.40
7 purchase totals =	$983.72		$1,060.1594	$1,060.17	$1,060.10	$1,060.20