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	$150.39	12.245%	$168.8053	$168.81	$168.80	$168.80
Purchase #2	$110.54	12.263%	$124.0955	$124.10	$124.10	$124.10
Purchase #3	$160.89	5.419%	$169.6086	$169.61	$169.60	$169.60
Purchase #4	$237.88	9.255%	$259.8958	$259.90	$259.90	$259.90
Purchase #5	$148.37	5.307%	$156.244	$156.24	$156.25	$156.20
Purchase #6	$38.69	5.317%	$40.7471	$40.75	$40.75	$40.70
Purchase #7	$85.73	10.622%	$94.8362	$94.84	$94.85	$94.80
7 purchase totals =	$932.49		$1,014.2325	$1,014.25	$1,014.25	$1,014.10