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	$50.73	10.819%	$56.2185	$56.22	$56.20	$56.20
Purchase #2	$47.61	4.252%	$49.6344	$49.63	$49.65	$49.60
Purchase #3	$88.39	8.126%	$95.5726	$95.57	$95.55	$95.60
Purchase #4	$52.80	12.816%	$59.5668	$59.57	$59.55	$59.60
Purchase #5	$159.94	6.691%	$170.6416	$170.64	$170.65	$170.60
Purchase #6	$106.76	4.156%	$111.1969	$111.20	$111.20	$111.20
Purchase #7	$192.33	8.524%	$208.7242	$208.72	$208.70	$208.70
7 purchase totals =	$698.56		$751.5550	$751.55	$751.50	$751.50