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	$100.64	6.544%	$107.2259	$107.23	$107.25	$107.20
Purchase #2	$36.34	11.550%	$40.5373	$40.54	$40.55	$40.50
Purchase #3	$167.67	3.764%	$173.9811	$173.98	$174.00	$174.00
Purchase #4	$50.64	6.484%	$53.9235	$53.92	$53.90	$53.90
Purchase #5	$198.58	8.592%	$215.642	$215.64	$215.65	$215.60
Purchase #6	$83.54	8.185%	$90.3777	$90.38	$90.40	$90.40
Purchase #7	$31.82	4.448%	$33.2354	$33.24	$33.25	$33.20
7 purchase totals =	$669.23		$714.9229	$714.93	$715.00	$714.80