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	$59.55	13.874%	$67.812	$67.81	$67.80	$67.80
Purchase #2	$110.75	11.721%	$123.731	$123.73	$123.75	$123.70
Purchase #3	$25.89	5.111%	$27.2132	$27.21	$27.20	$27.20
Purchase #4	$210.69	13.384%	$238.8887	$238.89	$238.90	$238.90
Purchase #5	$123.89	3.107%	$127.7393	$127.74	$127.75	$127.70
Purchase #6	$213.65	10.197%	$235.4359	$235.44	$235.45	$235.40
Purchase #7	$226.65	12.571%	$255.1422	$255.14	$255.15	$255.10
7 purchase totals =	$971.07		$1,075.9623	$1,075.96	$1,076.00	$1,075.80