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	$209.69	3.447%	$216.918	$216.92	$216.90	$216.90
Purchase #2	$49.80	7.822%	$53.6954	$53.70	$53.70	$53.70
Purchase #3	$125.88	5.284%	$132.5315	$132.53	$132.55	$132.50
Purchase #4	$168.59	8.501%	$182.9218	$182.92	$182.90	$182.90
Purchase #5	$80.72	3.729%	$83.73	$83.73	$83.75	$83.70
Purchase #6	$103.43	7.647%	$111.3393	$111.34	$111.35	$111.30
Purchase #7	$182.29	6.166%	$193.53	$193.53	$193.55	$193.50
7 purchase totals =	$920.40		$974.6660	$974.67	$974.70	$974.50