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	$38.59	8.128%	$41.7266	$41.73	$41.75	$41.70
Purchase #2	$202.72	7.762%	$218.4551	$218.46	$218.45	$218.50
Purchase #3	$18.95	4.149%	$19.7362	$19.74	$19.75	$19.70
Purchase #4	$167.28	3.257%	$172.7283	$172.73	$172.75	$172.70
Purchase #5	$174.33	4.681%	$182.4904	$182.49	$182.50	$182.50
Purchase #6	$141.42	10.305%	$155.9933	$155.99	$156.00	$156.00
Purchase #7	$103.54	7.476%	$111.2807	$111.28	$111.30	$111.30
7 purchase totals =	$846.83		$902.4106	$902.42	$902.50	$902.40