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	$168.46	12.276%	$189.1401	$189.14	$189.15	$189.10
Purchase #2	$233.84	9.254%	$255.4796	$255.48	$255.50	$255.50
Purchase #3	$13.78	12.165%	$15.4563	$15.46	$15.45	$15.50
Purchase #4	$221.80	12.458%	$249.4318	$249.43	$249.45	$249.40
Purchase #5	$101.95	9.742%	$111.882	$111.88	$111.90	$111.90
Purchase #6	$203.61	11.571%	$227.1697	$227.17	$227.15	$227.20
Purchase #7	$162.81	10.717%	$180.2583	$180.26	$180.25	$180.30
7 purchase totals =	$1,106.25		$1,228.8178	$1,228.82	$1,228.85	$1,228.90