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	$106.67	4.128%	$111.0733	$111.07	$111.05	$111.10
Purchase #2	$97.26	9.841%	$106.8314	$106.83	$106.85	$106.80
Purchase #3	$191.72	13.427%	$217.4622	$217.46	$217.45	$217.50
Purchase #4	$246.56	9.301%	$269.4925	$269.49	$269.50	$269.50
Purchase #5	$223.46	9.553%	$244.8071	$244.81	$244.80	$244.80
Purchase #6	$119.56	10.230%	$131.791	$131.79	$131.80	$131.80
Purchase #7	$68.96	8.782%	$75.0161	$75.02	$75.00	$75.00
7 purchase totals =	$1,054.19		$1,156.4736	$1,156.47	$1,156.45	$1,156.50