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	$55.57	3.293%	$57.3999	$57.40	$57.40	$57.40
Purchase #2	$232.94	13.191%	$263.6671	$263.67	$263.65	$263.70
Purchase #3	$99.73	5.294%	$105.0097	$105.01	$105.00	$105.00
Purchase #4	$143.76	11.647%	$160.5037	$160.50	$160.50	$160.50
Purchase #5	$48.32	6.566%	$51.4927	$51.49	$51.50	$51.50
Purchase #6	$238.73	12.238%	$267.9458	$267.95	$267.95	$267.90
Purchase #7	$137.83	5.296%	$145.1295	$145.13	$145.15	$145.10
7 purchase totals =	$956.88		$1,051.1484	$1,051.15	$1,051.15	$1,051.10