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	$97.37	8.393%	$105.5423	$105.54	$105.55	$105.50
Purchase #2	$205.75	9.678%	$225.6625	$225.66	$225.65	$225.70
Purchase #3	$43.91	7.602%	$47.248	$47.25	$47.25	$47.20
Purchase #4	$187.32	9.198%	$204.5497	$204.55	$204.55	$204.50
Purchase #5	$7.64	4.178%	$7.9592	$7.96	$7.95	$8.00
Purchase #6	$90.57	9.835%	$99.4776	$99.48	$99.50	$99.50
Purchase #7	$64.34	5.424%	$67.8298	$67.83	$67.85	$67.80
7 purchase totals =	$696.90		$758.2691	$758.27	$758.30	$758.20