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	$103.69	7.576%	$111.5456	$111.55	$111.55	$111.50
Purchase #2	$197.93	5.807%	$209.4238	$209.42	$209.40	$209.40
Purchase #3	$123.88	8.272%	$134.1274	$134.13	$134.15	$134.10
Purchase #4	$232.45	10.795%	$257.543	$257.54	$257.55	$257.50
Purchase #5	$57.28	6.756%	$61.1498	$61.15	$61.15	$61.10
Purchase #6	$143.95	7.746%	$155.1004	$155.10	$155.10	$155.10
Purchase #7	$152.46	7.822%	$164.3854	$164.39	$164.40	$164.40
7 purchase totals =	$1,011.64		$1,093.2754	$1,093.28	$1,093.30	$1,093.10