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	$163.33	6.573%	$174.0657	$174.07	$174.05	$174.10
Purchase #2	$97.59	5.858%	$103.3068	$103.31	$103.30	$103.30
Purchase #3	$160.93	7.105%	$172.3641	$172.36	$172.35	$172.40
Purchase #4	$46.62	10.296%	$51.42	$51.42	$51.40	$51.40
Purchase #5	$78.74	4.263%	$82.0967	$82.10	$82.10	$82.10
Purchase #6	$88.57	11.768%	$98.9929	$98.99	$99.00	$99.00
Purchase #7	$130.30	9.702%	$142.9417	$142.94	$142.95	$142.90
7 purchase totals =	$766.08		$825.1879	$825.19	$825.15	$825.20