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	$234.66	10.487%	$259.2688	$259.27	$259.25	$259.30
Purchase #2	$196.48	10.380%	$216.8746	$216.87	$216.85	$216.90
Purchase #3	$186.83	5.364%	$196.8516	$196.85	$196.85	$196.90
Purchase #4	$160.73	12.508%	$180.8341	$180.83	$180.85	$180.80
Purchase #5	$33.90	5.145%	$35.6442	$35.64	$35.65	$35.60
Purchase #6	$203.62	9.404%	$222.7684	$222.77	$222.75	$222.80
Purchase #7	$14.25	11.853%	$15.9391	$15.94	$15.95	$15.90
7 purchase totals =	$1,030.47		$1,128.1808	$1,128.17	$1,128.15	$1,128.20