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	$78.52	8.307%	$85.0427	$85.04	$85.05	$85.00
Purchase #2	$63.92	11.472%	$71.2529	$71.25	$71.25	$71.30
Purchase #3	$215.88	4.381%	$225.3377	$225.34	$225.35	$225.30
Purchase #4	$161.57	3.846%	$167.784	$167.78	$167.80	$167.80
Purchase #5	$192.73	8.582%	$209.2701	$209.27	$209.25	$209.30
Purchase #6	$225.97	5.280%	$237.9012	$237.90	$237.90	$237.90
Purchase #7	$38.86	4.180%	$40.4843	$40.48	$40.50	$40.50
7 purchase totals =	$977.45		$1,037.0729	$1,037.06	$1,037.10	$1,037.10