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	$109.81	4.134%	$114.3495	$114.35	$114.35	$114.30
Purchase #2	$89.32	5.765%	$94.4693	$94.47	$94.45	$94.50
Purchase #3	$200.41	9.559%	$219.5672	$219.57	$219.55	$219.60
Purchase #4	$248.64	3.325%	$256.9073	$256.91	$256.90	$256.90
Purchase #5	$21.49	11.152%	$23.8866	$23.89	$23.90	$23.90
Purchase #6	$238.28	10.177%	$262.5298	$262.53	$262.55	$262.50
Purchase #7	$115.90	9.596%	$127.0218	$127.02	$127.00	$127.00
7 purchase totals =	$1,023.85		$1,098.7315	$1,098.74	$1,098.70	$1,098.70