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	$230.53	12.457%	$259.2471	$259.25	$259.25	$259.20
Purchase #2	$104.68	8.398%	$113.471	$113.47	$113.45	$113.50
Purchase #3	$41.92	3.869%	$43.5419	$43.54	$43.55	$43.50
Purchase #4	$111.63	11.194%	$124.1259	$124.13	$124.15	$124.10
Purchase #5	$250.97	5.143%	$263.8774	$263.88	$263.90	$263.90
Purchase #6	$50.94	4.650%	$53.3087	$53.31	$53.30	$53.30
Purchase #7	$174.94	8.874%	$190.4642	$190.46	$190.45	$190.50
7 purchase totals =	$965.61		$1,048.0362	$1,048.04	$1,048.05	$1,048.00