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	$76.68	13.640%	$87.1392	$87.14	$87.15	$87.10
Purchase #2	$64.34	11.522%	$71.7533	$71.75	$71.75	$71.80
Purchase #3	$203.70	9.624%	$223.3041	$223.30	$223.30	$223.30
Purchase #4	$219.32	13.870%	$249.7397	$249.74	$249.75	$249.70
Purchase #5	$187.69	10.245%	$206.9188	$206.92	$206.90	$206.90
Purchase #6	$127.39	11.228%	$141.6933	$141.69	$141.70	$141.70
Purchase #7	$78.52	8.651%	$85.3128	$85.31	$85.30	$85.30
7 purchase totals =	$957.64		$1,065.8612	$1,065.85	$1,065.85	$1,065.80