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	$193.76	10.393%	$213.8975	$213.90	$213.90	$213.90
Purchase #2	$57.33	10.835%	$63.5417	$63.54	$63.55	$63.50
Purchase #3	$243.39	9.124%	$265.5969	$265.60	$265.60	$265.60
Purchase #4	$123.65	3.824%	$128.3784	$128.38	$128.40	$128.40
Purchase #5	$165.70	7.500%	$178.1275	$178.13	$178.15	$178.10
Purchase #6	$169.60	13.117%	$191.8464	$191.85	$191.85	$191.80
Purchase #7	$127.54	8.540%	$138.4319	$138.43	$138.45	$138.40
7 purchase totals =	$1,080.97		$1,179.8203	$1,179.83	$1,179.90	$1,179.70