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	$42.62	9.592%	$46.7081	$46.71	$46.70	$46.70
Purchase #2	$202.27	10.199%	$222.8995	$222.90	$222.90	$222.90
Purchase #3	$111.86	12.295%	$125.6132	$125.61	$125.60	$125.60
Purchase #4	$115.81	6.393%	$123.2137	$123.21	$123.20	$123.20
Purchase #5	$103.54	4.196%	$107.8845	$107.88	$107.90	$107.90
Purchase #6	$233.46	9.201%	$254.9407	$254.94	$254.95	$254.90
Purchase #7	$49.76	3.221%	$51.3628	$51.36	$51.35	$51.40
7 purchase totals =	$859.32		$932.6225	$932.61	$932.60	$932.60