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	$175.89	13.432%	$199.5155	$199.52	$199.50	$199.50
Purchase #2	$223.97	8.736%	$243.536	$243.54	$243.55	$243.50
Purchase #3	$216.40	5.302%	$227.8735	$227.87	$227.85	$227.90
Purchase #4	$154.45	9.260%	$168.7521	$168.75	$168.75	$168.80
Purchase #5	$180.64	8.804%	$196.5435	$196.54	$196.55	$196.50
Purchase #6	$29.56	5.301%	$31.127	$31.13	$31.15	$31.10
Purchase #7	$135.93	8.398%	$147.3454	$147.35	$147.35	$147.30
7 purchase totals =	$1,116.84		$1,214.6930	$1,214.70	$1,214.70	$1,214.60