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	$78.48	13.721%	$89.2482	$89.25	$89.25	$89.20
Purchase #2	$120.72	9.296%	$131.9421	$131.94	$131.95	$131.90
Purchase #3	$5.66	11.806%	$6.3282	$6.33	$6.35	$6.30
Purchase #4	$139.87	10.398%	$154.4137	$154.41	$154.40	$154.40
Purchase #5	$95.64	11.374%	$106.5181	$106.52	$106.50	$106.50
Purchase #6	$125.65	13.189%	$142.222	$142.22	$142.20	$142.20
Purchase #7	$241.33	5.154%	$253.7681	$253.77	$253.75	$253.80
7 purchase totals =	$807.35		$884.4404	$884.44	$884.40	$884.30