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	$30.42	10.210%	$33.5259	$33.53	$33.55	$33.50
Purchase #2	$217.51	3.199%	$224.4681	$224.47	$224.45	$224.50
Purchase #3	$79.46	13.819%	$90.4406	$90.44	$90.45	$90.40
Purchase #4	$224.86	12.524%	$253.0215	$253.02	$253.00	$253.00
Purchase #5	$219.25	13.369%	$248.5615	$248.56	$248.55	$248.60
Purchase #6	$93.67	12.434%	$105.3169	$105.32	$105.30	$105.30
Purchase #7	$102.41	4.651%	$107.1731	$107.17	$107.15	$107.20
7 purchase totals =	$967.58		$1,062.5076	$1,062.51	$1,062.45	$1,062.50