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	$54.69	13.564%	$62.1082	$62.11	$62.10	$62.10
Purchase #2	$221.32	12.869%	$249.8017	$249.80	$249.80	$249.80
Purchase #3	$47.68	5.600%	$50.3501	$50.35	$50.35	$50.40
Purchase #4	$220.84	13.434%	$250.5076	$250.51	$250.50	$250.50
Purchase #5	$112.61	13.547%	$127.8653	$127.87	$127.85	$127.90
Purchase #6	$131.51	9.762%	$144.348	$144.35	$144.35	$144.30
Purchase #7	$77.46	6.175%	$82.2432	$82.24	$82.25	$82.20
7 purchase totals =	$866.11		$967.2241	$967.23	$967.20	$967.20