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	$12.78	11.550%	$14.2561	$14.26	$14.25	$14.30
Purchase #2	$220.94	9.225%	$241.3217	$241.32	$241.30	$241.30
Purchase #3	$181.52	4.747%	$190.1368	$190.14	$190.15	$190.10
Purchase #4	$112.47	5.637%	$118.8099	$118.81	$118.80	$118.80
Purchase #5	$93.33	9.757%	$102.4362	$102.44	$102.45	$102.40
Purchase #6	$174.76	7.270%	$187.4651	$187.47	$187.45	$187.50
Purchase #7	$41.68	3.451%	$43.1184	$43.12	$43.10	$43.10
7 purchase totals =	$837.48		$897.5442	$897.56	$897.50	$897.50