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	$102.31	12.289%	$114.8829	$114.88	$114.90	$114.90
Purchase #2	$70.33	11.301%	$78.278	$78.28	$78.30	$78.30
Purchase #3	$139.55	12.822%	$157.4431	$157.44	$157.45	$157.40
Purchase #4	$7.60	12.685%	$8.5641	$8.56	$8.55	$8.60
Purchase #5	$101.45	13.585%	$115.232	$115.23	$115.25	$115.20
Purchase #6	$179.58	9.523%	$196.6814	$196.68	$196.70	$196.70
Purchase #7	$61.30	10.612%	$67.8052	$67.81	$67.80	$67.80
7 purchase totals =	$662.12		$738.8867	$738.88	$738.95	$738.90