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	$179.67	4.257%	$187.3186	$187.32	$187.30	$187.30
Purchase #2	$229.32	5.762%	$242.5334	$242.53	$242.55	$242.50
Purchase #3	$119.75	6.429%	$127.4487	$127.45	$127.45	$127.40
Purchase #4	$34.31	4.620%	$35.8951	$35.90	$35.90	$35.90
Purchase #5	$51.98	3.280%	$53.6849	$53.68	$53.70	$53.70
Purchase #6	$219.75	12.355%	$246.9001	$246.90	$246.90	$246.90
Purchase #7	$130.52	7.662%	$140.5204	$140.52	$140.50	$140.50
7 purchase totals =	$965.30		$1,034.3012	$1,034.30	$1,034.30	$1,034.20