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	$74.71	5.521%	$78.8347	$78.83	$78.85	$78.80
Purchase #2	$185.94	4.766%	$194.8019	$194.80	$194.80	$194.80
Purchase #3	$199.92	6.172%	$212.2591	$212.26	$212.25	$212.30
Purchase #4	$94.44	12.669%	$106.4046	$106.40	$106.40	$106.40
Purchase #5	$214.54	9.462%	$234.8398	$234.84	$234.85	$234.80
Purchase #6	$145.82	11.686%	$162.8605	$162.86	$162.85	$162.90
Purchase #7	$187.71	3.625%	$194.5145	$194.51	$194.50	$194.50
7 purchase totals =	$1,103.08		$1,184.5151	$1,184.50	$1,184.50	$1,184.50