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	$186.50	13.443%	$211.5712	$211.57	$211.55	$211.60
Purchase #2	$194.39	13.835%	$221.2839	$221.28	$221.30	$221.30
Purchase #3	$154.42	6.809%	$164.9345	$164.93	$164.95	$164.90
Purchase #4	$96.85	8.550%	$105.1307	$105.13	$105.15	$105.10
Purchase #5	$125.39	12.506%	$141.0713	$141.07	$141.05	$141.10
Purchase #6	$6.69	13.131%	$7.5685	$7.57	$7.55	$7.60
Purchase #7	$240.78	3.679%	$249.6383	$249.64	$249.65	$249.60
7 purchase totals =	$1,005.02		$1,101.1984	$1,101.19	$1,101.20	$1,101.20