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	$164.52	10.337%	$181.5264	$181.53	$181.55	$181.50
Purchase #2	$239.53	6.791%	$255.7965	$255.80	$255.80	$255.80
Purchase #3	$195.83	12.696%	$220.6926	$220.69	$220.70	$220.70
Purchase #4	$146.78	10.767%	$162.5838	$162.58	$162.60	$162.60
Purchase #5	$80.41	13.817%	$91.5202	$91.52	$91.50	$91.50
Purchase #6	$21.88	13.220%	$24.7725	$24.77	$24.75	$24.80
Purchase #7	$38.75	6.809%	$41.3885	$41.39	$41.40	$41.40
7 purchase totals =	$887.70		$978.2805	$978.28	$978.30	$978.30