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	$133.54	12.686%	$150.4809	$150.48	$150.50	$150.50
Purchase #2	$238.30	3.550%	$246.7597	$246.76	$246.75	$246.80
Purchase #3	$160.76	11.654%	$179.495	$179.50	$179.50	$179.50
Purchase #4	$36.40	7.485%	$39.1245	$39.12	$39.10	$39.10
Purchase #5	$114.94	4.480%	$120.0893	$120.09	$120.10	$120.10
Purchase #6	$94.93	10.109%	$104.5265	$104.53	$104.55	$104.50
Purchase #7	$205.47	7.418%	$220.7118	$220.71	$220.70	$220.70
7 purchase totals =	$984.34		$1,061.1877	$1,061.19	$1,061.20	$1,061.20