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	$163.61	5.635%	$172.8294	$172.83	$172.85	$172.80
Purchase #2	$175.52	12.164%	$196.8703	$196.87	$196.85	$196.90
Purchase #3	$196.55	13.729%	$223.5343	$223.53	$223.55	$223.50
Purchase #4	$50.34	9.645%	$55.1953	$55.20	$55.20	$55.20
Purchase #5	$205.82	3.698%	$213.4312	$213.43	$213.45	$213.40
Purchase #6	$103.68	6.220%	$110.1289	$110.13	$110.15	$110.10
Purchase #7	$149.48	6.428%	$159.0886	$159.09	$159.10	$159.10
7 purchase totals =	$1,045.00		$1,131.0780	$1,131.08	$1,131.15	$1,131.00