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	$149.95	9.567%	$164.2957	$164.30	$164.30	$164.30
Purchase #2	$174.53	6.146%	$185.2566	$185.26	$185.25	$185.30
Purchase #3	$170.75	7.396%	$183.3787	$183.38	$183.40	$183.40
Purchase #4	$210.61	5.735%	$222.6885	$222.69	$222.70	$222.70
Purchase #5	$71.25	12.867%	$80.4177	$80.42	$80.40	$80.40
Purchase #6	$145.39	7.630%	$156.4833	$156.48	$156.50	$156.50
Purchase #7	$208.37	9.378%	$227.9109	$227.91	$227.90	$227.90
7 purchase totals =	$1,130.85		$1,220.4314	$1,220.44	$1,220.45	$1,220.50