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	$53.85	10.547%	$59.5296	$59.53	$59.55	$59.50
Purchase #2	$96.37	5.338%	$101.5142	$101.51	$101.50	$101.50
Purchase #3	$245.70	5.751%	$259.8302	$259.83	$259.85	$259.80
Purchase #4	$235.58	3.716%	$244.3342	$244.33	$244.35	$244.30
Purchase #5	$51.83	5.839%	$54.8564	$54.86	$54.85	$54.90
Purchase #6	$169.48	12.191%	$190.1413	$190.14	$190.15	$190.10
Purchase #7	$203.57	3.592%	$210.8822	$210.88	$210.90	$210.90
7 purchase totals =	$1,056.38		$1,121.0881	$1,121.08	$1,121.15	$1,121.00