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	$64.35	10.264%	$70.9549	$70.95	$70.95	$71.00
Purchase #2	$58.59	4.535%	$61.2471	$61.25	$61.25	$61.20
Purchase #3	$242.88	13.257%	$275.0786	$275.08	$275.10	$275.10
Purchase #4	$236.67	3.320%	$244.5274	$244.53	$244.55	$244.50
Purchase #5	$145.52	11.555%	$162.3348	$162.33	$162.35	$162.30
Purchase #6	$230.78	6.696%	$246.233	$246.23	$246.25	$246.20
Purchase #7	$94.70	9.704%	$103.8897	$103.89	$103.90	$103.90
7 purchase totals =	$1,073.49		$1,164.2655	$1,164.26	$1,164.35	$1,164.20