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	$122.59	3.816%	$127.268	$127.27	$127.25	$127.30
Purchase #2	$21.25	9.412%	$23.2501	$23.25	$23.25	$23.30
Purchase #3	$168.28	10.343%	$185.6852	$185.69	$185.70	$185.70
Purchase #4	$100.37	3.511%	$103.894	$103.89	$103.90	$103.90
Purchase #5	$229.64	5.743%	$242.8282	$242.83	$242.85	$242.80
Purchase #6	$114.88	7.733%	$123.7637	$123.76	$123.75	$123.80
Purchase #7	$147.83	8.715%	$160.7134	$160.71	$160.70	$160.70
7 purchase totals =	$904.84		$967.4026	$967.40	$967.40	$967.50