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	$208.75	6.562%	$222.4482	$222.45	$222.45	$222.40
Purchase #2	$127.77	4.832%	$133.9438	$133.94	$133.95	$133.90
Purchase #3	$215.78	3.236%	$222.7626	$222.76	$222.75	$222.80
Purchase #4	$190.94	4.499%	$199.5304	$199.53	$199.55	$199.50
Purchase #5	$15.83	3.105%	$16.3215	$16.32	$16.30	$16.30
Purchase #6	$35.49	11.847%	$39.6945	$39.69	$39.70	$39.70
Purchase #7	$154.36	7.873%	$166.5128	$166.51	$166.50	$166.50
7 purchase totals =	$948.92		$1,001.2138	$1,001.20	$1,001.20	$1,001.10