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	$20.81	7.364%	$22.3424	$22.34	$22.35	$22.30
Purchase #2	$227.95	5.862%	$241.3124	$241.31	$241.30	$241.30
Purchase #3	$120.27	5.745%	$127.1795	$127.18	$127.20	$127.20
Purchase #4	$190.61	13.548%	$216.4338	$216.43	$216.45	$216.40
Purchase #5	$168.48	4.306%	$175.7347	$175.73	$175.75	$175.70
Purchase #6	$71.31	10.408%	$78.7319	$78.73	$78.75	$78.70
Purchase #7	$236.93	7.663%	$255.0859	$255.09	$255.10	$255.10
7 purchase totals =	$1,036.36		$1,116.8206	$1,116.81	$1,116.90	$1,116.70