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	$233.92	11.858%	$261.6582	$261.66	$261.65	$261.70
Purchase #2	$200.32	7.446%	$215.2358	$215.24	$215.25	$215.20
Purchase #3	$164.33	12.240%	$184.444	$184.44	$184.45	$184.40
Purchase #4	$41.56	4.510%	$43.4344	$43.43	$43.45	$43.40
Purchase #5	$53.42	10.614%	$59.09	$59.09	$59.10	$59.10
Purchase #6	$128.66	10.466%	$142.1256	$142.13	$142.15	$142.10
Purchase #7	$121.87	7.381%	$130.8652	$130.87	$130.85	$130.90
7 purchase totals =	$944.08		$1,036.8532	$1,036.86	$1,036.90	$1,036.80