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	$194.52	11.703%	$217.2847	$217.28	$217.30	$217.30
Purchase #2	$224.55	7.213%	$240.7468	$240.75	$240.75	$240.70
Purchase #3	$196.79	6.610%	$209.7978	$209.80	$209.80	$209.80
Purchase #4	$232.64	3.464%	$240.6986	$240.70	$240.70	$240.70
Purchase #5	$118.98	7.480%	$127.8797	$127.88	$127.90	$127.90
Purchase #6	$82.86	8.256%	$89.7009	$89.70	$89.70	$89.70
Purchase #7	$141.95	13.426%	$161.0082	$161.01	$161.00	$161.00
7 purchase totals =	$1,192.29		$1,287.1167	$1,287.12	$1,287.15	$1,287.10