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	$124.43	8.174%	$134.6009	$134.60	$134.60	$134.60
Purchase #2	$54.43	5.515%	$57.4318	$57.43	$57.45	$57.40
Purchase #3	$116.38	7.185%	$124.7419	$124.74	$124.75	$124.70
Purchase #4	$112.39	4.847%	$117.8375	$117.84	$117.85	$117.80
Purchase #5	$190.48	3.359%	$196.8782	$196.88	$196.90	$196.90
Purchase #6	$220.53	6.146%	$234.0838	$234.08	$234.10	$234.10
Purchase #7	$134.69	6.571%	$143.5405	$143.54	$143.55	$143.50
7 purchase totals =	$953.33		$1,009.1146	$1,009.11	$1,009.20	$1,009.00