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	$248.92	5.195%	$261.8514	$261.85	$261.85	$261.90
Purchase #2	$37.91	8.199%	$41.0182	$41.02	$41.00	$41.00
Purchase #3	$97.73	8.309%	$105.8504	$105.85	$105.85	$105.90
Purchase #4	$127.32	9.239%	$139.0831	$139.08	$139.10	$139.10
Purchase #5	$201.92	8.418%	$218.9176	$218.92	$218.90	$218.90
Purchase #6	$190.77	3.158%	$196.7945	$196.79	$196.80	$196.80
Purchase #7	$85.73	5.270%	$90.248	$90.25	$90.25	$90.20
7 purchase totals =	$990.30		$1,053.7632	$1,053.76	$1,053.75	$1,053.80