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	$132.94	5.223%	$139.8835	$139.88	$139.90	$139.90
Purchase #2	$50.36	12.185%	$56.4964	$56.50	$56.50	$56.50
Purchase #3	$65.54	8.351%	$71.0132	$71.01	$71.00	$71.00
Purchase #4	$139.34	7.178%	$149.3418	$149.34	$149.35	$149.30
Purchase #5	$47.73	6.754%	$50.9537	$50.95	$50.95	$51.00
Purchase #6	$137.69	12.187%	$154.4703	$154.47	$154.45	$154.50
Purchase #7	$114.34	11.697%	$127.7143	$127.71	$127.70	$127.70
7 purchase totals =	$687.94		$749.8732	$749.86	$749.85	$749.90