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	$100.64	10.497%	$111.2042	$111.20	$111.20	$111.20
Purchase #2	$240.26	5.661%	$253.8611	$253.86	$253.85	$253.90
Purchase #3	$208.84	12.480%	$234.9032	$234.90	$234.90	$234.90
Purchase #4	$241.70	6.467%	$257.3307	$257.33	$257.35	$257.30
Purchase #5	$6.75	10.520%	$7.4601	$7.46	$7.45	$7.50
Purchase #6	$86.26	11.450%	$96.1368	$96.14	$96.15	$96.10
Purchase #7	$83.85	12.185%	$94.0671	$94.07	$94.05	$94.10
7 purchase totals =	$968.30		$1,054.9632	$1,054.96	$1,054.95	$1,055.00