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	$47.38	12.806%	$53.4475	$53.45	$53.45	$53.40
Purchase #2	$86.29	4.419%	$90.1032	$90.10	$90.10	$90.10
Purchase #3	$143.72	6.312%	$152.7916	$152.79	$152.80	$152.80
Purchase #4	$156.55	5.284%	$164.8221	$164.82	$164.80	$164.80
Purchase #5	$54.31	9.703%	$59.5797	$59.58	$59.60	$59.60
Purchase #6	$8.70	5.570%	$9.1846	$9.18	$9.20	$9.20
Purchase #7	$27.92	12.772%	$31.4859	$31.49	$31.50	$31.50
7 purchase totals =	$524.87		$561.4146	$561.41	$561.45	$561.40