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	$88.49	7.615%	$95.2285	$95.23	$95.25	$95.20
Purchase #2	$248.64	13.492%	$282.1865	$282.19	$282.20	$282.20
Purchase #3	$127.45	9.248%	$139.2366	$139.24	$139.25	$139.20
Purchase #4	$248.98	6.535%	$265.2508	$265.25	$265.25	$265.30
Purchase #5	$188.46	6.357%	$200.4404	$200.44	$200.45	$200.40
Purchase #6	$140.83	7.711%	$151.6894	$151.69	$151.70	$151.70
Purchase #7	$153.67	11.494%	$171.3328	$171.33	$171.35	$171.30
7 purchase totals =	$1,196.52		$1,305.3650	$1,305.37	$1,305.45	$1,305.30