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	$138.87	5.761%	$146.8703	$146.87	$146.85	$146.90
Purchase #2	$92.89	12.767%	$104.7493	$104.75	$104.75	$104.70
Purchase #3	$208.38	7.531%	$224.0731	$224.07	$224.05	$224.10
Purchase #4	$79.77	7.166%	$85.4863	$85.49	$85.50	$85.50
Purchase #5	$70.57	11.399%	$78.6143	$78.61	$78.60	$78.60
Purchase #6	$209.53	4.424%	$218.7996	$218.80	$218.80	$218.80
Purchase #7	$165.32	12.668%	$186.2627	$186.26	$186.25	$186.30
7 purchase totals =	$965.33		$1,044.8556	$1,044.85	$1,044.80	$1,044.90