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	$199.47	11.710%	$222.8279	$222.83	$222.85	$222.80
Purchase #2	$133.30	13.354%	$151.1009	$151.10	$151.10	$151.10
Purchase #3	$120.77	9.271%	$131.9666	$131.97	$131.95	$132.00
Purchase #4	$162.26	10.327%	$179.0166	$179.02	$179.00	$179.00
Purchase #5	$79.49	3.428%	$82.2149	$82.21	$82.20	$82.20
Purchase #6	$172.85	12.392%	$194.2696	$194.27	$194.25	$194.30
Purchase #7	$223.29	13.553%	$253.5525	$253.55	$253.55	$253.60
7 purchase totals =	$1,091.43		$1,214.9490	$1,214.95	$1,214.90	$1,215.00