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	$40.44	7.339%	$43.4079	$43.41	$43.40	$43.40
Purchase #2	$95.45	8.217%	$103.2931	$103.29	$103.30	$103.30
Purchase #3	$245.27	4.611%	$256.5794	$256.58	$256.60	$256.60
Purchase #4	$80.95	5.377%	$85.3027	$85.30	$85.30	$85.30
Purchase #5	$189.90	12.136%	$212.9463	$212.95	$212.95	$212.90
Purchase #6	$137.80	5.267%	$145.0579	$145.06	$145.05	$145.10
Purchase #7	$229.28	11.671%	$256.0393	$256.04	$256.05	$256.00
7 purchase totals =	$1,019.09		$1,102.6266	$1,102.63	$1,102.65	$1,102.60