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	$212.94	12.484%	$239.5234	$239.52	$239.50	$239.50
Purchase #2	$229.27	9.324%	$250.6471	$250.65	$250.65	$250.60
Purchase #3	$118.73	7.204%	$127.2833	$127.28	$127.30	$127.30
Purchase #4	$89.85	8.631%	$97.605	$97.61	$97.60	$97.60
Purchase #5	$77.44	6.344%	$82.3528	$82.35	$82.35	$82.40
Purchase #6	$46.60	8.496%	$50.5591	$50.56	$50.55	$50.60
Purchase #7	$194.94	9.189%	$212.853	$212.85	$212.85	$212.90
7 purchase totals =	$969.77		$1,060.8237	$1,060.82	$1,060.80	$1,060.90