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	$57.39	3.278%	$59.2712	$59.27	$59.25	$59.30
Purchase #2	$173.48	8.793%	$188.7341	$188.73	$188.75	$188.70
Purchase #3	$173.78	8.455%	$188.4731	$188.47	$188.45	$188.50
Purchase #4	$171.52	3.146%	$176.916	$176.92	$176.90	$176.90
Purchase #5	$116.56	5.767%	$123.282	$123.28	$123.30	$123.30
Purchase #6	$79.77	9.859%	$87.6345	$87.63	$87.65	$87.60
Purchase #7	$205.77	7.498%	$221.1986	$221.20	$221.20	$221.20
7 purchase totals =	$978.27		$1,045.5095	$1,045.50	$1,045.50	$1,045.50