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	$12.57	11.145%	$13.9709	$13.97	$13.95	$14.00
Purchase #2	$219.85	4.175%	$229.0287	$229.03	$229.05	$229.00
Purchase #3	$142.85	6.323%	$151.8824	$151.88	$151.90	$151.90
Purchase #4	$184.41	7.613%	$198.4491	$198.45	$198.45	$198.40
Purchase #5	$115.91	13.293%	$131.3179	$131.32	$131.30	$131.30
Purchase #6	$87.87	4.450%	$91.7802	$91.78	$91.80	$91.80
Purchase #7	$37.83	4.285%	$39.451	$39.45	$39.45	$39.50
7 purchase totals =	$801.29		$855.8802	$855.88	$855.90	$855.90