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	$204.76	9.554%	$224.3228	$224.32	$224.30	$224.30
Purchase #2	$91.26	11.409%	$101.6719	$101.67	$101.65	$101.70
Purchase #3	$103.43	7.611%	$111.3021	$111.30	$111.30	$111.30
Purchase #4	$207.86	3.486%	$215.106	$215.11	$215.10	$215.10
Purchase #5	$93.70	12.206%	$105.137	$105.14	$105.15	$105.10
Purchase #6	$18.55	8.483%	$20.1236	$20.12	$20.10	$20.10
Purchase #7	$141.62	6.778%	$151.219	$151.22	$151.20	$151.20
7 purchase totals =	$861.18		$928.8824	$928.88	$928.80	$928.80