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	$57.85	13.839%	$65.8559	$65.86	$65.85	$65.90
Purchase #2	$53.72	3.523%	$55.6126	$55.61	$55.60	$55.60
Purchase #3	$78.93	6.190%	$83.8158	$83.82	$83.80	$83.80
Purchase #4	$247.27	9.615%	$271.045	$271.05	$271.05	$271.00
Purchase #5	$100.85	10.417%	$111.3555	$111.36	$111.35	$111.40
Purchase #6	$208.95	8.190%	$226.063	$226.06	$226.05	$226.10
Purchase #7	$218.26	11.459%	$243.2704	$243.27	$243.25	$243.30
7 purchase totals =	$965.83		$1,057.0182	$1,057.03	$1,056.95	$1,057.10