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	$103.73	10.500%	$114.6217	$114.62	$114.60	$114.60
Purchase #2	$196.62	8.592%	$213.5136	$213.51	$213.50	$213.50
Purchase #3	$143.63	11.756%	$160.5151	$160.52	$160.50	$160.50
Purchase #4	$47.42	11.730%	$52.9824	$52.98	$53.00	$53.00
Purchase #5	$93.92	5.666%	$99.2415	$99.24	$99.25	$99.20
Purchase #6	$174.85	4.402%	$182.5469	$182.55	$182.55	$182.50
Purchase #7	$26.64	6.296%	$28.3173	$28.32	$28.30	$28.30
7 purchase totals =	$786.81		$851.7385	$851.74	$851.70	$851.60