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	$63.59	13.693%	$72.2974	$72.30	$72.30	$72.30
Purchase #2	$126.31	8.149%	$136.603	$136.60	$136.60	$136.60
Purchase #3	$209.86	13.621%	$238.445	$238.45	$238.45	$238.40
Purchase #4	$75.58	5.218%	$79.5238	$79.52	$79.50	$79.50
Purchase #5	$174.47	12.623%	$196.4933	$196.49	$196.50	$196.50
Purchase #6	$185.88	13.410%	$210.8065	$210.81	$210.80	$210.80
Purchase #7	$84.75	8.407%	$91.8749	$91.87	$91.85	$91.90
7 purchase totals =	$920.44		$1,026.0439	$1,026.04	$1,026.00	$1,026.00