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	$134.85	11.475%	$150.324	$150.32	$150.30	$150.30
Purchase #2	$194.48	3.295%	$200.8881	$200.89	$200.90	$200.90
Purchase #3	$15.74	11.488%	$17.5482	$17.55	$17.55	$17.50
Purchase #4	$92.95	7.264%	$99.7019	$99.70	$99.70	$99.70
Purchase #5	$221.34	10.471%	$244.5165	$244.52	$244.50	$244.50
Purchase #6	$167.43	8.783%	$182.1354	$182.14	$182.15	$182.10
Purchase #7	$87.83	4.207%	$91.525	$91.53	$91.55	$91.50
7 purchase totals =	$914.62		$986.6391	$986.65	$986.65	$986.50