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	$219.66	9.302%	$240.0928	$240.09	$240.10	$240.10
Purchase #2	$193.39	3.399%	$199.9633	$199.96	$199.95	$200.00
Purchase #3	$40.65	4.837%	$42.6162	$42.62	$42.60	$42.60
Purchase #4	$52.78	12.162%	$59.1991	$59.20	$59.20	$59.20
Purchase #5	$49.51	12.153%	$55.527	$55.53	$55.55	$55.50
Purchase #6	$79.82	8.655%	$86.7284	$86.73	$86.75	$86.70
Purchase #7	$140.86	3.784%	$146.1901	$146.19	$146.20	$146.20
7 purchase totals =	$776.67		$830.3169	$830.32	$830.35	$830.30