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	$72.70	3.432%	$75.1951	$75.20	$75.20	$75.20
Purchase #2	$118.89	7.483%	$127.7865	$127.79	$127.80	$127.80
Purchase #3	$37.38	9.578%	$40.9603	$40.96	$40.95	$41.00
Purchase #4	$196.40	10.768%	$217.5484	$217.55	$217.55	$217.50
Purchase #5	$94.48	5.696%	$99.8616	$99.86	$99.85	$99.90
Purchase #6	$229.59	4.330%	$239.5312	$239.53	$239.55	$239.50
Purchase #7	$175.85	13.543%	$199.6654	$199.67	$199.65	$199.70
7 purchase totals =	$925.29		$1,000.5485	$1,000.56	$1,000.55	$1,000.60