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	$47.72	9.108%	$52.0663	$52.07	$52.05	$52.10
Purchase #2	$161.94	3.398%	$167.4427	$167.44	$167.45	$167.40
Purchase #3	$167.42	4.811%	$175.4746	$175.47	$175.45	$175.50
Purchase #4	$211.61	9.463%	$231.6347	$231.63	$231.65	$231.60
Purchase #5	$117.44	9.481%	$128.5745	$128.57	$128.55	$128.60
Purchase #6	$12.48	9.270%	$13.6369	$13.64	$13.65	$13.60
Purchase #7	$114.78	11.121%	$127.5447	$127.54	$127.55	$127.50
7 purchase totals =	$833.39		$896.3744	$896.36	$896.35	$896.30