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	$118.64	12.448%	$133.4083	$133.41	$133.40	$133.40
Purchase #2	$48.83	7.523%	$52.5035	$52.50	$52.50	$52.50
Purchase #3	$104.75	7.198%	$112.2899	$112.29	$112.30	$112.30
Purchase #4	$202.89	3.445%	$209.8796	$209.88	$209.90	$209.90
Purchase #5	$227.52	12.324%	$255.5596	$255.56	$255.55	$255.60
Purchase #6	$104.26	6.432%	$110.966	$110.97	$110.95	$111.00
Purchase #7	$102.84	8.488%	$111.5691	$111.57	$111.55	$111.60
7 purchase totals =	$909.73		$986.1760	$986.18	$986.15	$986.30