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	$109.73	8.151%	$118.6741	$118.67	$118.65	$118.70
Purchase #2	$69.26	13.352%	$78.5076	$78.51	$78.50	$78.50
Purchase #3	$123.71	13.588%	$140.5197	$140.52	$140.50	$140.50
Purchase #4	$41.65	9.370%	$45.5526	$45.55	$45.55	$45.60
Purchase #5	$194.50	11.412%	$216.6963	$216.70	$216.70	$216.70
Purchase #6	$226.27	4.708%	$236.9228	$236.92	$236.90	$236.90
Purchase #7	$161.61	11.359%	$179.9673	$179.97	$179.95	$180.00
7 purchase totals =	$926.73		$1,016.8404	$1,016.84	$1,016.75	$1,016.90