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	$174.39	12.752%	$196.6282	$196.63	$196.65	$196.60
Purchase #2	$36.83	6.182%	$39.1068	$39.11	$39.10	$39.10
Purchase #3	$155.63	8.700%	$169.1698	$169.17	$169.15	$169.20
Purchase #4	$5.98	12.313%	$6.7163	$6.72	$6.70	$6.70
Purchase #5	$96.32	4.267%	$100.43	$100.43	$100.45	$100.40
Purchase #6	$244.78	13.648%	$278.1876	$278.19	$278.20	$278.20
Purchase #7	$169.60	8.524%	$184.0567	$184.06	$184.05	$184.10
7 purchase totals =	$883.53		$974.2954	$974.31	$974.30	$974.30