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	$141.73	3.663%	$146.9216	$146.92	$146.90	$146.90
Purchase #2	$26.34	3.758%	$27.3299	$27.33	$27.35	$27.30
Purchase #3	$88.60	3.768%	$91.9384	$91.94	$91.95	$91.90
Purchase #4	$134.93	13.780%	$153.5234	$153.52	$153.50	$153.50
Purchase #5	$142.95	9.440%	$156.4445	$156.44	$156.45	$156.40
Purchase #6	$102.38	8.709%	$111.2963	$111.30	$111.30	$111.30
Purchase #7	$70.34	4.666%	$73.6221	$73.62	$73.60	$73.60
7 purchase totals =	$707.27		$761.0762	$761.07	$761.05	$760.90