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	$117.25	8.745%	$127.5035	$127.50	$127.50	$127.50
Purchase #2	$46.78	9.719%	$51.3265	$51.33	$51.35	$51.30
Purchase #3	$203.90	8.811%	$221.8656	$221.87	$221.85	$221.90
Purchase #4	$91.88	4.208%	$95.7463	$95.75	$95.75	$95.70
Purchase #5	$196.71	12.486%	$221.2712	$221.27	$221.25	$221.30
Purchase #6	$209.34	4.281%	$218.3018	$218.30	$218.30	$218.30
Purchase #7	$160.61	11.776%	$179.5234	$179.52	$179.50	$179.50
7 purchase totals =	$1,026.47		$1,115.5383	$1,115.54	$1,115.50	$1,115.50