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	$178.43	8.260%	$193.1683	$193.17	$193.15	$193.20
Purchase #2	$117.91	8.103%	$127.4642	$127.46	$127.45	$127.50
Purchase #3	$245.70	5.636%	$259.5477	$259.55	$259.55	$259.50
Purchase #4	$96.57	6.324%	$102.6771	$102.68	$102.70	$102.70
Purchase #5	$67.67	13.305%	$76.6735	$76.67	$76.65	$76.70
Purchase #6	$48.36	13.641%	$54.9568	$54.96	$54.95	$55.00
Purchase #7	$171.76	10.855%	$190.4045	$190.40	$190.40	$190.40
7 purchase totals =	$926.40		$1,004.8921	$1,004.89	$1,004.85	$1,005.00