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	$149.39	13.583%	$169.6816	$169.68	$169.70	$169.70
Purchase #2	$145.53	7.871%	$156.9847	$156.98	$157.00	$157.00
Purchase #3	$34.58	3.586%	$35.82	$35.82	$35.80	$35.80
Purchase #4	$232.74	4.334%	$242.827	$242.83	$242.85	$242.80
Purchase #5	$229.45	9.143%	$250.4286	$250.43	$250.45	$250.40
Purchase #6	$97.94	12.190%	$109.8789	$109.88	$109.90	$109.90
Purchase #7	$111.64	7.278%	$119.7652	$119.77	$119.75	$119.80
7 purchase totals =	$1,001.27		$1,085.3860	$1,085.39	$1,085.45	$1,085.40