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	$190.63	6.544%	$203.1048	$203.10	$203.10	$203.10
Purchase #2	$123.57	3.324%	$127.6775	$127.68	$127.70	$127.70
Purchase #3	$143.78	10.501%	$158.8783	$158.88	$158.90	$158.90
Purchase #4	$167.78	13.553%	$190.5192	$190.52	$190.50	$190.50
Purchase #5	$48.54	12.744%	$54.7259	$54.73	$54.75	$54.70
Purchase #6	$245.71	12.603%	$276.6768	$276.68	$276.70	$276.70
Purchase #7	$113.97	5.449%	$120.1802	$120.18	$120.20	$120.20
7 purchase totals =	$1,033.98		$1,131.7627	$1,131.77	$1,131.85	$1,131.80