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	$43.82	4.708%	$45.883	$45.88	$45.90	$45.90
Purchase #2	$54.99	13.208%	$62.2531	$62.25	$62.25	$62.30
Purchase #3	$98.39	4.121%	$102.4447	$102.44	$102.45	$102.40
Purchase #4	$191.85	13.555%	$217.8553	$217.86	$217.85	$217.90
Purchase #5	$244.50	4.272%	$254.945	$254.95	$254.95	$254.90
Purchase #6	$187.59	12.700%	$211.4139	$211.41	$211.40	$211.40
Purchase #7	$87.43	4.843%	$91.6642	$91.66	$91.65	$91.70
7 purchase totals =	$908.57		$986.4592	$986.45	$986.45	$986.50