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	$130.32	8.216%	$141.0271	$141.03	$141.05	$141.00
Purchase #2	$141.30	9.413%	$154.6006	$154.60	$154.60	$154.60
Purchase #3	$148.56	7.786%	$160.1269	$160.13	$160.15	$160.10
Purchase #4	$34.70	7.786%	$37.4017	$37.40	$37.40	$37.40
Purchase #5	$177.56	6.108%	$188.4054	$188.41	$188.40	$188.40
Purchase #6	$85.80	6.552%	$91.4216	$91.42	$91.40	$91.40
Purchase #7	$102.65	5.275%	$108.0648	$108.06	$108.05	$108.10
7 purchase totals =	$820.89		$881.0481	$881.05	$881.05	$881.00