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	$182.95	7.259%	$196.2303	$196.23	$196.25	$196.20
Purchase #2	$111.94	6.790%	$119.5407	$119.54	$119.55	$119.50
Purchase #3	$49.91	6.347%	$53.0778	$53.08	$53.10	$53.10
Purchase #4	$169.61	5.734%	$179.3354	$179.34	$179.35	$179.30
Purchase #5	$246.59	4.375%	$257.3783	$257.38	$257.40	$257.40
Purchase #6	$93.39	7.825%	$100.6978	$100.70	$100.70	$100.70
Purchase #7	$44.41	12.496%	$49.9595	$49.96	$49.95	$50.00
7 purchase totals =	$898.80		$956.2198	$956.23	$956.30	$956.20