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	$196.49	13.716%	$223.4406	$223.44	$223.45	$223.40
Purchase #2	$240.63	6.810%	$257.0169	$257.02	$257.00	$257.00
Purchase #3	$115.56	12.396%	$129.8848	$129.88	$129.90	$129.90
Purchase #4	$124.43	5.789%	$131.6333	$131.63	$131.65	$131.60
Purchase #5	$160.78	8.542%	$174.5138	$174.51	$174.50	$174.50
Purchase #6	$78.39	11.237%	$87.1987	$87.20	$87.20	$87.20
Purchase #7	$38.54	11.289%	$42.8908	$42.89	$42.90	$42.90
7 purchase totals =	$954.82		$1,046.5789	$1,046.57	$1,046.60	$1,046.50