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	$75.31	10.274%	$83.0473	$83.05	$83.05	$83.00
Purchase #2	$174.51	6.767%	$186.3191	$186.32	$186.30	$186.30
Purchase #3	$228.57	5.474%	$241.0819	$241.08	$241.10	$241.10
Purchase #4	$82.79	9.359%	$90.5383	$90.54	$90.55	$90.50
Purchase #5	$36.79	10.141%	$40.5209	$40.52	$40.50	$40.50
Purchase #6	$85.88	12.251%	$96.4012	$96.40	$96.40	$96.40
Purchase #7	$190.29	8.516%	$206.4951	$206.50	$206.50	$206.50
7 purchase totals =	$874.14		$944.4038	$944.41	$944.40	$944.30