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	$111.70	12.380%	$125.5285	$125.53	$125.55	$125.50
Purchase #2	$155.96	5.636%	$164.7499	$164.75	$164.75	$164.70
Purchase #3	$142.64	8.356%	$154.559	$154.56	$154.55	$154.60
Purchase #4	$59.37	3.860%	$61.6617	$61.66	$61.65	$61.70
Purchase #5	$203.85	3.683%	$211.3578	$211.36	$211.35	$211.40
Purchase #6	$33.40	12.286%	$37.5035	$37.50	$37.50	$37.50
Purchase #7	$67.38	7.337%	$72.3237	$72.32	$72.30	$72.30
7 purchase totals =	$774.30		$827.6841	$827.68	$827.65	$827.70