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	$120.64	5.340%	$127.0822	$127.08	$127.10	$127.10
Purchase #2	$106.35	11.811%	$118.911	$118.91	$118.90	$118.90
Purchase #3	$57.54	11.387%	$64.0921	$64.09	$64.10	$64.10
Purchase #4	$222.91	3.403%	$230.4956	$230.50	$230.50	$230.50
Purchase #5	$173.35	3.556%	$179.5143	$179.51	$179.50	$179.50
Purchase #6	$35.69	7.669%	$38.4271	$38.43	$38.45	$38.40
Purchase #7	$236.59	12.829%	$266.9421	$266.94	$266.95	$266.90
7 purchase totals =	$953.07		$1,025.4644	$1,025.46	$1,025.50	$1,025.40