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	$131.44	12.839%	$148.3156	$148.32	$148.30	$148.30
Purchase #2	$100.74	8.585%	$109.3885	$109.39	$109.40	$109.40
Purchase #3	$240.59	3.801%	$249.7348	$249.73	$249.75	$249.70
Purchase #4	$197.37	9.257%	$215.6405	$215.64	$215.65	$215.60
Purchase #5	$63.77	13.813%	$72.5786	$72.58	$72.60	$72.60
Purchase #6	$183.78	6.742%	$196.1704	$196.17	$196.15	$196.20
Purchase #7	$186.29	12.416%	$209.4198	$209.42	$209.40	$209.40
7 purchase totals =	$1,103.98		$1,201.2482	$1,201.25	$1,201.25	$1,201.20