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	$186.28	5.799%	$197.0824	$197.08	$197.10	$197.10
Purchase #2	$110.28	12.310%	$123.8555	$123.86	$123.85	$123.90
Purchase #3	$162.86	12.547%	$183.294	$183.29	$183.30	$183.30
Purchase #4	$79.93	3.119%	$82.423	$82.42	$82.40	$82.40
Purchase #5	$112.83	9.313%	$123.3379	$123.34	$123.35	$123.30
Purchase #6	$236.96	5.462%	$249.9028	$249.90	$249.90	$249.90
Purchase #7	$187.93	8.753%	$204.3795	$204.38	$204.40	$204.40
7 purchase totals =	$1,077.07		$1,164.2751	$1,164.27	$1,164.30	$1,164.30