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	$186.58	12.292%	$209.5144	$209.51	$209.50	$209.50
Purchase #2	$81.48	4.467%	$85.1197	$85.12	$85.10	$85.10
Purchase #3	$74.54	6.682%	$79.5208	$79.52	$79.50	$79.50
Purchase #4	$190.90	3.760%	$198.0778	$198.08	$198.10	$198.10
Purchase #5	$132.72	3.317%	$137.1223	$137.12	$137.10	$137.10
Purchase #6	$154.83	4.323%	$161.5233	$161.52	$161.50	$161.50
Purchase #7	$59.47	6.116%	$63.1072	$63.11	$63.10	$63.10
7 purchase totals =	$880.52		$933.9855	$933.98	$933.90	$933.90