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	$147.83	8.443%	$160.3113	$160.31	$160.30	$160.30
Purchase #2	$156.85	11.537%	$174.9458	$174.95	$174.95	$174.90
Purchase #3	$233.75	9.220%	$255.3018	$255.30	$255.30	$255.30
Purchase #4	$223.28	5.862%	$236.3687	$236.37	$236.35	$236.40
Purchase #5	$241.28	6.410%	$256.746	$256.75	$256.75	$256.70
Purchase #6	$128.69	11.421%	$143.3877	$143.39	$143.40	$143.40
Purchase #7	$81.27	10.746%	$90.0033	$90.00	$90.00	$90.00
7 purchase totals =	$1,212.95		$1,317.0646	$1,317.07	$1,317.05	$1,317.00