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	$200.52	11.524%	$223.6279	$223.63	$223.65	$223.60
Purchase #2	$56.37	12.814%	$63.5933	$63.59	$63.60	$63.60
Purchase #3	$5.52	9.364%	$6.0369	$6.04	$6.05	$6.00
Purchase #4	$120.32	4.845%	$126.1495	$126.15	$126.15	$126.10
Purchase #5	$209.42	11.690%	$233.9012	$233.90	$233.90	$233.90
Purchase #6	$48.90	13.313%	$55.4101	$55.41	$55.40	$55.40
Purchase #7	$234.25	12.653%	$263.8897	$263.89	$263.90	$263.90
7 purchase totals =	$875.30		$972.6086	$972.61	$972.65	$972.50