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	$41.30	6.153%	$43.8412	$43.84	$43.85	$43.80
Purchase #2	$151.95	12.748%	$171.3206	$171.32	$171.30	$171.30
Purchase #3	$116.25	10.153%	$128.0529	$128.05	$128.05	$128.10
Purchase #4	$134.46	5.474%	$141.8203	$141.82	$141.80	$141.80
Purchase #5	$55.53	6.568%	$59.1772	$59.18	$59.20	$59.20
Purchase #6	$142.80	5.367%	$150.4641	$150.46	$150.45	$150.50
Purchase #7	$35.57	6.268%	$37.7995	$37.80	$37.80	$37.80
7 purchase totals =	$677.86		$732.4758	$732.47	$732.45	$732.50