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	$124.94	5.543%	$131.8654	$131.87	$131.85	$131.90
Purchase #2	$139.64	7.342%	$149.8924	$149.89	$149.90	$149.90
Purchase #3	$140.47	11.440%	$156.5398	$156.54	$156.55	$156.50
Purchase #4	$245.35	13.421%	$278.2784	$278.28	$278.30	$278.30
Purchase #5	$177.95	12.154%	$199.578	$199.58	$199.60	$199.60
Purchase #6	$94.27	11.401%	$105.0177	$105.02	$105.00	$105.00
Purchase #7	$21.80	11.121%	$24.2244	$24.22	$24.20	$24.20
7 purchase totals =	$944.42		$1,045.3961	$1,045.40	$1,045.40	$1,045.40