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	$240.87	8.193%	$260.6045	$260.60	$260.60	$260.60
Purchase #2	$199.71	11.829%	$223.3337	$223.33	$223.35	$223.30
Purchase #3	$123.86	5.820%	$131.0687	$131.07	$131.05	$131.10
Purchase #4	$5.86	11.638%	$6.542	$6.54	$6.55	$6.50
Purchase #5	$129.93	8.227%	$140.6193	$140.62	$140.60	$140.60
Purchase #6	$145.40	3.719%	$150.8074	$150.81	$150.80	$150.80
Purchase #7	$246.42	6.443%	$262.2968	$262.30	$262.30	$262.30
7 purchase totals =	$1,092.05		$1,175.2724	$1,175.27	$1,175.25	$1,175.20