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	$47.56	9.585%	$52.1186	$52.12	$52.10	$52.10
Purchase #2	$104.38	10.762%	$115.6134	$115.61	$115.60	$115.60
Purchase #3	$183.27	7.819%	$197.5999	$197.60	$197.60	$197.60
Purchase #4	$10.36	5.802%	$10.9611	$10.96	$10.95	$11.00
Purchase #5	$164.48	6.337%	$174.9031	$174.90	$174.90	$174.90
Purchase #6	$100.42	3.795%	$104.2309	$104.23	$104.25	$104.20
Purchase #7	$82.55	10.163%	$90.9396	$90.94	$90.95	$90.90
7 purchase totals =	$693.02		$746.3666	$746.36	$746.35	$746.30