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	$153.37	4.556%	$160.3575	$160.36	$160.35	$160.40
Purchase #2	$79.80	5.743%	$84.3829	$84.38	$84.40	$84.40
Purchase #3	$249.96	12.549%	$281.3275	$281.33	$281.35	$281.30
Purchase #4	$136.65	7.831%	$147.3511	$147.35	$147.35	$147.40
Purchase #5	$179.84	9.444%	$196.8241	$196.82	$196.80	$196.80
Purchase #6	$76.87	4.573%	$80.3853	$80.39	$80.40	$80.40
Purchase #7	$97.31	13.646%	$110.5889	$110.59	$110.60	$110.60
7 purchase totals =	$973.80		$1,061.2173	$1,061.22	$1,061.25	$1,061.30