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	$183.52	3.518%	$189.9762	$189.98	$190.00	$190.00
Purchase #2	$147.25	3.856%	$152.928	$152.93	$152.95	$152.90
Purchase #3	$134.86	6.302%	$143.3589	$143.36	$143.35	$143.40
Purchase #4	$56.55	11.122%	$62.8395	$62.84	$62.85	$62.80
Purchase #5	$219.75	13.456%	$249.3196	$249.32	$249.30	$249.30
Purchase #6	$193.30	3.214%	$199.5127	$199.51	$199.50	$199.50
Purchase #7	$152.39	4.290%	$158.9275	$158.93	$158.95	$158.90
7 purchase totals =	$1,087.62		$1,156.8624	$1,156.87	$1,156.90	$1,156.80