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	$139.90	7.660%	$150.6163	$150.62	$150.60	$150.60
Purchase #2	$54.64	12.632%	$61.5421	$61.54	$61.55	$61.50
Purchase #3	$94.97	12.411%	$106.7567	$106.76	$106.75	$106.80
Purchase #4	$104.32	6.756%	$111.3679	$111.37	$111.35	$111.40
Purchase #5	$204.57	9.215%	$223.4211	$223.42	$223.40	$223.40
Purchase #6	$131.85	3.649%	$136.6612	$136.66	$136.65	$136.70
Purchase #7	$195.32	13.855%	$222.3816	$222.38	$222.40	$222.40
7 purchase totals =	$925.57		$1,012.7469	$1,012.75	$1,012.70	$1,012.80