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	$57.66	3.559%	$59.7121	$59.71	$59.70	$59.70
Purchase #2	$23.64	13.594%	$26.8536	$26.85	$26.85	$26.90
Purchase #3	$196.55	12.138%	$220.4072	$220.41	$220.40	$220.40
Purchase #4	$127.28	13.412%	$144.3508	$144.35	$144.35	$144.40
Purchase #5	$56.75	10.696%	$62.82	$62.82	$62.80	$62.80
Purchase #6	$169.63	8.401%	$183.8806	$183.88	$183.90	$183.90
Purchase #7	$67.39	5.227%	$70.9125	$70.91	$70.90	$70.90
7 purchase totals =	$698.90		$768.9368	$768.93	$768.90	$769.00