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	$229.72	13.830%	$261.4903	$261.49	$261.50	$261.50
Purchase #2	$205.60	12.304%	$230.897	$230.90	$230.90	$230.90
Purchase #3	$117.33	13.674%	$133.3737	$133.37	$133.35	$133.40
Purchase #4	$79.43	4.339%	$82.8765	$82.88	$82.90	$82.90
Purchase #5	$114.75	9.391%	$125.5262	$125.53	$125.55	$125.50
Purchase #6	$118.56	7.803%	$127.8112	$127.81	$127.80	$127.80
Purchase #7	$67.32	7.464%	$72.3448	$72.34	$72.35	$72.30
7 purchase totals =	$932.71		$1,034.3197	$1,034.32	$1,034.35	$1,034.30