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	$53.77	10.531%	$59.4325	$59.43	$59.45	$59.40
Purchase #2	$159.95	5.276%	$168.389	$168.39	$168.40	$168.40
Purchase #3	$97.82	6.764%	$104.4365	$104.44	$104.45	$104.40
Purchase #4	$18.97	12.494%	$21.3401	$21.34	$21.35	$21.30
Purchase #5	$47.60	7.191%	$51.0229	$51.02	$51.00	$51.00
Purchase #6	$245.39	13.730%	$279.082	$279.08	$279.10	$279.10
Purchase #7	$168.95	12.130%	$189.4436	$189.44	$189.45	$189.40
7 purchase totals =	$792.45		$873.1466	$873.14	$873.20	$873.00