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	$146.66	10.501%	$162.0608	$162.06	$162.05	$162.10
Purchase #2	$240.46	9.357%	$262.9598	$262.96	$262.95	$263.00
Purchase #3	$56.27	5.487%	$59.3575	$59.36	$59.35	$59.40
Purchase #4	$88.51	6.819%	$94.5455	$94.55	$94.55	$94.50
Purchase #5	$111.58	5.406%	$117.612	$117.61	$117.60	$117.60
Purchase #6	$27.74	13.691%	$31.5379	$31.54	$31.55	$31.50
Purchase #7	$179.85	9.216%	$196.425	$196.43	$196.45	$196.40
7 purchase totals =	$851.07		$924.4985	$924.51	$924.50	$924.50