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	$47.83	10.605%	$52.9024	$52.90	$52.90	$52.90
Purchase #2	$237.36	8.326%	$257.1226	$257.12	$257.10	$257.10
Purchase #3	$138.83	13.810%	$158.0024	$158.00	$158.00	$158.00
Purchase #4	$12.60	6.456%	$13.4135	$13.41	$13.40	$13.40
Purchase #5	$40.38	6.533%	$43.018	$43.02	$43.00	$43.00
Purchase #6	$73.81	12.300%	$82.8886	$82.89	$82.90	$82.90
Purchase #7	$188.46	4.410%	$196.7711	$196.77	$196.75	$196.80
7 purchase totals =	$739.27		$804.1186	$804.11	$804.05	$804.10