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	$62.76	8.548%	$68.1247	$68.12	$68.10	$68.10
Purchase #2	$46.49	3.558%	$48.1441	$48.14	$48.15	$48.10
Purchase #3	$164.47	9.646%	$180.3348	$180.33	$180.35	$180.30
Purchase #4	$210.84	13.162%	$238.5908	$238.59	$238.60	$238.60
Purchase #5	$158.76	10.576%	$175.5505	$175.55	$175.55	$175.60
Purchase #6	$106.44	4.592%	$111.3277	$111.33	$111.35	$111.30
Purchase #7	$196.78	3.402%	$203.4745	$203.47	$203.45	$203.50
7 purchase totals =	$946.54		$1,025.5471	$1,025.53	$1,025.55	$1,025.50