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	$116.94	8.265%	$126.6051	$126.61	$126.60	$126.60
Purchase #2	$210.53	6.591%	$224.406	$224.41	$224.40	$224.40
Purchase #3	$62.43	7.232%	$66.9449	$66.94	$66.95	$66.90
Purchase #4	$84.78	7.600%	$91.2233	$91.22	$91.20	$91.20
Purchase #5	$238.58	8.521%	$258.9094	$258.91	$258.90	$258.90
Purchase #6	$236.83	5.798%	$250.5614	$250.56	$250.55	$250.60
Purchase #7	$70.58	11.258%	$78.5259	$78.53	$78.55	$78.50
7 purchase totals =	$1,020.67		$1,097.1760	$1,097.18	$1,097.15	$1,097.10