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	$188.90	5.575%	$199.4312	$199.43	$199.45	$199.40
Purchase #2	$212.30	3.155%	$218.9981	$219.00	$219.00	$219.00
Purchase #3	$142.67	12.527%	$160.5423	$160.54	$160.55	$160.50
Purchase #4	$112.87	8.835%	$122.8421	$122.84	$122.85	$122.80
Purchase #5	$81.55	10.656%	$90.24	$90.24	$90.25	$90.20
Purchase #6	$81.64	10.127%	$89.9077	$89.91	$89.90	$89.90
Purchase #7	$110.84	11.673%	$123.7784	$123.78	$123.80	$123.80
7 purchase totals =	$930.77		$1,005.7398	$1,005.74	$1,005.80	$1,005.60