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	$68.28	6.410%	$72.6567	$72.66	$72.65	$72.70
Purchase #2	$10.99	4.270%	$11.4593	$11.46	$11.45	$11.50
Purchase #3	$218.74	12.697%	$246.5134	$246.51	$246.50	$246.50
Purchase #4	$174.47	6.844%	$186.4107	$186.41	$186.40	$186.40
Purchase #5	$241.68	3.482%	$250.0953	$250.10	$250.10	$250.10
Purchase #6	$172.51	4.113%	$179.6053	$179.61	$179.60	$179.60
Purchase #7	$52.91	7.183%	$56.7105	$56.71	$56.70	$56.70
7 purchase totals =	$939.58		$1,003.4512	$1,003.46	$1,003.40	$1,003.50