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	$237.27	7.342%	$254.6904	$254.69	$254.70	$254.70
Purchase #2	$249.29	3.848%	$258.8827	$258.88	$258.90	$258.90
Purchase #3	$78.79	9.826%	$86.5319	$86.53	$86.55	$86.50
Purchase #4	$187.97	4.184%	$195.8347	$195.83	$195.85	$195.80
Purchase #5	$52.46	4.851%	$55.0048	$55.00	$55.00	$55.00
Purchase #6	$179.35	6.539%	$191.0777	$191.08	$191.10	$191.10
Purchase #7	$113.82	12.309%	$127.8301	$127.83	$127.85	$127.80
7 purchase totals =	$1,098.95		$1,169.8523	$1,169.84	$1,169.95	$1,169.80