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	$183.71	12.210%	$206.141	$206.14	$206.15	$206.10
Purchase #2	$78.33	9.764%	$85.9781	$85.98	$86.00	$86.00
Purchase #3	$226.72	11.764%	$253.3913	$253.39	$253.40	$253.40
Purchase #4	$36.32	13.725%	$41.3049	$41.30	$41.30	$41.30
Purchase #5	$180.80	10.328%	$199.473	$199.47	$199.45	$199.50
Purchase #6	$134.66	12.252%	$151.1585	$151.16	$151.15	$151.20
Purchase #7	$102.37	11.266%	$113.903	$113.90	$113.90	$113.90
7 purchase totals =	$942.91		$1,051.3498	$1,051.34	$1,051.35	$1,051.40