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	$185.96	10.710%	$205.8763	$205.88	$205.90	$205.90
Purchase #2	$76.30	8.184%	$82.5444	$82.54	$82.55	$82.50
Purchase #3	$140.77	4.639%	$147.3003	$147.30	$147.30	$147.30
Purchase #4	$22.76	4.803%	$23.8532	$23.85	$23.85	$23.90
Purchase #5	$111.95	13.505%	$127.0688	$127.07	$127.05	$127.10
Purchase #6	$178.97	4.367%	$186.7856	$186.79	$186.80	$186.80
Purchase #7	$9.49	10.339%	$10.4712	$10.47	$10.45	$10.50
7 purchase totals =	$726.20		$783.8998	$783.90	$783.90	$784.00