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	$74.71	11.183%	$83.0648	$83.06	$83.05	$83.10
Purchase #2	$135.75	4.464%	$141.8099	$141.81	$141.80	$141.80
Purchase #3	$191.66	10.621%	$212.0162	$212.02	$212.00	$212.00
Purchase #4	$37.32	4.294%	$38.9225	$38.92	$38.90	$38.90
Purchase #5	$111.25	4.362%	$116.1027	$116.10	$116.10	$116.10
Purchase #6	$184.45	3.663%	$191.2064	$191.21	$191.20	$191.20
Purchase #7	$72.71	7.594%	$78.2316	$78.23	$78.25	$78.20
7 purchase totals =	$807.85		$861.3541	$861.35	$861.30	$861.30